Sonic CD

Playable characters

• Sonic the Hedgehog

Non-playable characters

• Amy Rose (first appearance)
• Dr. Eggman
• Metal Sonic (first appearance)
• Miles “Tails” Prower (cameo)
• Animals
  • Flicky
  • Pecky
  • Pocky
  • Ricky
  • Robin (first appearance)
  • Sheep (first appearance)
  • Unnamed red fish (only appearance)
  • Unnamed teal fish (only appearance)
  • Unnamed white bird (only appearance)
  • Unnamed yellow bird (only appearance)

Enemies

1. Palmtree Panic: A vibrant tropical environment set against the backdrop of lush mountains and cascading waterfalls.
   • Past: Transports players to a prehistoric landscape, evoking a sense of primordial beauty and untouched nature.
   • Bad Future: Enveloped in a grim industrial haze, the level becomes a mechanized wasteland with polluted air and contaminated waters.
   • Good Future: Retains the mechanized elements but juxtaposes them with a harmonious blend of vivid colors, clean surroundings, and flourishing flora.
2. Collision Chaos: A unique amalgamation of mechanized forest and a sprawling casino area, complete with a distinct “reflection” feature.
   • Past: Presents a surreal, orange-toned forest, contributing to an otherworldly atmosphere.
   • Bad Future: Takes on an eerie and desolate appearance with gray machinery casting a somber pall.
   • Good Future: Radiates a bright, pink-and-blue futuristic ambiance, creating a lively and inviting atmosphere.
3. Tidal Tempest: Submerged ruins situated at the foot of a volcanic structure, showcasing the impact of changing water levels over time.
   • Past: Immerses players in an underground cavern with minimal human intervention, save for the presence of pipes.
   • Bad Future: Depicts a deteriorating, polluted water plant, reflecting excessive industrialization.
   • Good Future: Transforms into a vibrant turquoise aquarium teeming with aquatic life and flourishing vegetation.
4. Quartz Quadrant: A bustling mine featuring conveyor belts and platforms, with its appearance evolving across different time Zones.
   • Past: Transports players to a swamp-like environment abundant with quartz and devoid of extensive technology.
   • Bad Future: Embraces a heavily mechanized, but quartz-less, mining operation.
   • Good Future: Unveils an underground golden-hued city, potentially crafted from quartz, exuding an air of opulence.
5. Wacky Workbench: An industrial zone nestled within a canyon, brimming with eccentric machinery and visual quirks.
   • Past: Offers a glimpse of the factory’s early construction stages.
   • Bad Future: Paints a grim picture of decay and corrosion amidst ruined machinery.
   • Good Future: Adorns the landscape with a palette of pink and purple, resembling a futuristic toy factory.
6. Stardust Speedway: A high-speed Round set on a massive highway illuminated by musical instruments, overlooking a sprawling cityscape.
   • Past: Transforms into an ancient, vine-covered Roman cityscape, showcasing minimal technological influence.
   • Bad Future: Evokes a sense of dystopia under a looming electrical storm, with a completed Eggman statue symbolizing control.
   • Good Future: Blossoms into a futuristic amusement park, marked by vibrant colors and the presence of an ornate cathedral.
7. Metallic Madness: Eggman’s operational base, laden with treacherous traps and advanced machinery.
   • Past: Depicts the base in the midst of construction, marked by towering cranes.
   • Bad Future: Portrays a decaying, desolate facility marred by neglect and ruin.
   • Good Future: Harmonizes machinery with nature, restoring a mechanized factory while integrating elements of the natural world.

In Sonic the Hedgehog CD, the Special Stages offer a unique three-dimensional environment where players must seek out and destroy UFOs to collect Time Stones. Here’s a breakdown of the mechanics and elements involved in the Special Stages:

1. Accessing Special Stages: To access a Special Stage, the player needs to collect and hold onto at least fifty Rings by the end of a Zone. A Giant Ring will appear above the Goal Plate, allowing the player to jump through and enter the Special Stage.
2. Objective: The main objective of a Special Stage is to destroy six UFOs scattered throughout the stage before the timer runs out. Each destroyed UFO provides a reward.
3. UFO Behavior: UFOs move in a sporadic and unpredictable manner, making them challenging to hit. Their movement patterns require players to use skill and timing to target and destroy them.
4. UFO Prizes: Destroying a UFO grants the player a reward. UFOs with yellow frames offer Ring Bonuses, increasing the player’s Ring count. UFOs with white frames provide temporary speed boosts, allowing Sonic to move faster.
5. Special Blue UFO: If the timer drops below twenty seconds, a unique blue UFO with red frames appears in the center of the stage. Destroying this UFO does not contribute to the UFO count but adds an extra thirty seconds to the timer.
6. Gimmicks and Obstacles: The Special Stage features various interactive elements:
   • Springs: Bounce Sonic upwards, aiding in reaching higher areas.
   • Bumpers: Bounce Sonic back upon contact, affecting his trajectory.
   • Fan Blocks: Cause Sonic to float temporarily when touched.
   • Chopper Blocks: Slow Sonic down and cause him to lose Rings if touched.
   • Dash Zones: Propel Sonic in different directions, influencing his movement.
7. Water Portions: Entering water areas within the Special Stage results in a ten-second deduction from the timer, adding an additional layer of challenge.
8. Completion and Scoring: After successfully completing or failing a Special Stage, the game calculates the obtained points and adds them to the player’s overall score. Once the Special Stage is concluded, the player returns to the main game and continues progressing through Zones.

1. EGG-HVC-001 (Palmtree Panic) (only appearance)
2. Egg Tilter (Collision Chaos) (only appearance)
3. Egg Bubble (Tidal Tempest) (only appearance)
4. Egg Conveyer (Quartz Quadrant) (only appearance)
5. Egg Razer (Wacky Workbench) (only appearance)
6. Metal Sonic (Stardust Speedway) (first appearance)
7. Egg Spinner (Metallic Madness) (only appearance)

Time Attack

The Time Attack mode in Sonic the Hedgehog CD operates similarly to its counterparts in other Sonic games. Accessed from the title menu, selecting Time Attack leads to a menu where a leaderboard showcases the fastest completion times for all completed Rounds within the main story mode.^[4]Sonic the Hedgehog CD (Sega CD) United States instruction booklet, pgs. 18-19. Additionally, a cumulative time for the entire game is presented beneath the Rounds, indicating the duration to finish the full game. In this mode, players can play through all three Zones of each Round, excluding Time Warp signs. Following the tradition of arcade leaderboards, Sonic the Hedgehog CD prompts players to input a three-character name upon achieving a new record.

Background

During the early 1990s, the popularity of compact discs (CDs) was on the rise as a storage medium for music and video games. In 1988, NEC, a rival of Sega, introduced the CD-ROM², an add-on for the TurboGrafx-16 console. At the 1991 Tokyo Game Show, Sega introduced the Sega CD, a CD-ROM expansion for the Mega Drive (Genesis) console. This add-on was released in Japan towards the end of 1991 and in the rest of the world between late 1992 and early 1993.^[5]strafefox (March 3, 2020). The Making of Sonic CD. YouTube. Retrieved on July 22, 2023.

In 1991, Sega achieved significant success with the release of Sonic the Hedgehog, a game that propelled the Mega Drive to compete with Nintendo’s SNES console. Following the success of Sonic 1, the lead programmer, Yuji Naka, became dissatisfied with the strict corporate policies at Sega of Japan. In response, he and a substantial portion of the original Sonic Team, responsible for the first game’s development, relocated to the United States to collaborate with the Sega Technical Institute (STI) on Sonic the Hedgehog 2.^[6]Linnenman, John (April 8, 2018). DF Retro: Sonic CD – under-appreciated but still brilliant today. Eurogamer. Retrieved on February 7, 2023.

Designer Naoto Ohshima also desired to join his colleagues in the United States, but the president of Sega convinced him to remain in Japan. This shift marked a significant transition in the Sonic series’ development.

Conception

Seizing the opportunity to build upon the success of Sonic 1, Sega aimed to create a new Sonic game specifically for the Sega CD platform, showcasing the capabilities of their innovative system. Naoto Ohshima emerged as one of the most qualified individuals to lead the development of this game, assuming the role of director. He then formed an entirely new development team, comprising Japanese developers with diverse backgrounds. Among these team members were individuals who had previously contributed to other notable games such as The Revenge of Shinobi, Golden Axe 2, and Streets of Rage.

One of the fresh faces on the team was Kazuyuki Hoshino, who took on the role of designer. Hoshino’s involvement in this project marked the beginning of his journey within the Sonic franchise, as he would later contribute to various other Sonic titles. This assembly of talent set the stage for the creation of a unique Sonic experience on the Sega CD platform

At first, we intended to use most of the elements from Sonic 2 and add new things with the possibilities offered by the CD (medium). But the more development progressed, the more different it became from Sonic 2, and we finally decided to make it a new title.

Naoto Ohshima on the initial concepts for Sonic CD^[7]“History”. The History of Sonic the Hedgehog. Les Editions Pix’n Love. September 6, 2013. pp. 44-45. ISBN 978-1-926778-96-9.

The pre-production phase of Sonic CD commenced in 1992, a period during which Sonic 2 was already in the midst of its development. Notably, Naoto Ohshima’s team enjoyed greater time and creative freedom compared to the Sonic Technical Institute (STI). They also experienced less pressure from Sega to meet strict release deadlines, a situation that Ohshima believed arose from the fact that they were not working on a traditional “numbered sequel” like their counterparts.^[8]Sheffield, Brandon (December 4, 2009). Out of the Blue: Naoto Ohshima Speaks. GameDeveloper. Retrieved on February 7, 2023.

Initially, the project was conceived as an enhanced port of Sonic 2 tailored for the Sega CD platform. The original intention was to leverage the core elements of Sonic 2 while integrating the new capabilities offered by the Sega CD. However, the development team’s vision gradually evolved, steering the project away from being a mere port and towards an entirely original creation. Consequently, the idea of a port was abandoned, and the decision was made to forge a fresh, standalone title.

The game was initially designated as “CD Sonic the Hedgehog”^[9]Electronic Gaming Monthly staff (March 1993). “CD Sonic the Hedgehog“. Electronic Gaming Monthly (44): 122. Archived from the original. Retrieved on February 7, 2023. (CDシーディーソニック・ザ・ヘッジホッグ Shīdī Sonikku za Hejjihoggu) before undergoing a name change that resulted in the final title, Sonic CD. This shift in direction allowed the team to craft a unique and innovative addition to the Sonic series.

Gameplay

While the original Sonic the Hedgehog game focused on combining platforming with its signature high-speed gameplay, Sonic CD took a different approach by emphasizing platforming and exploration. The core gameplay mechanics of the first Sonic game remained unchanged in Sonic CD, and the development team used the code from the original game as the foundation for their work on Sonic CD.

To enhance the gameplay and take advantage of the storage capacity of the Sega CD, the team brainstormed new concepts. One idea that emerged was the concept of time travel, which had actually been considered during the early development of Sonic 2 but was abandoned due to technical constraints.^[10]strafefox (May 22, 2018). The Making of Sonic the Hedgehog 2. YouTube. Retrieved on April 20, 2023. With more memory and time available for development on the Sega CD, the team decided to revisit and implement the time travel concept. This concept was also influenced by the sci-fi film “Back to the Future.”^[11]Sonic CD – Developer Interview Collection. Shmuplations.com. Retrieved on February 7, 2023.

In Sonic CD, four distinct time zones were created for each level. These zones were carefully designed to have unique level layouts while still being compatible with each other within the time travel mechanic.

Naoto Ohshima, the director of Sonic CD, initially aimed for a seamless transition between time zones, inspired by the instantaneous time travel sequences in “Back to the Future.” He envisioned a sonic boom effect that would instantly transform the level with a flash. However, technical limitations posed challenges. The Sega CD couldn’t directly access the Mega Drive RAM, which was necessary for the seamless transition. Instead, data had to be copied from the Mega Drive CPU and passed through other components, resulting in a noticeable slowdown. The development team ultimately concluded that achieving the intended instantaneous transition was not feasible, and a brief loading screen was implemented to mask the transition and hardware loading process.

The design of the Special Stages in Sonic CD initially aimed to build upon the Special Stages featured in the original Sonic the Hedgehog game. The intention was to utilize the Sega CD’s unique rotating function, which would require players to navigate through rotating mazes to locate the Time Stones. However, the development team found that the execution of this idea didn’t meet their expectations, particularly in terms of speed and gameplay dynamics.

In response, the team shifted their approach and envisioned a new concept for the Special Stages. This concept drew inspiration from the racing genre and aimed to create a race-style game mode that would fully showcase the capabilities of the Sega CD hardware. This change in direction was partly influenced by the recent release of Super Mario Kart,^[12]Masato Nishimura (March 19, 2012). まぢん on Twitter. Retrieved on February 9, 2023. “Masato Nakamura: そういやソニックCDのスペシャルステージも、開発初期の段階ではメガCDの回転機能を生かし、ソニック1のスペシャルステージを発展させた、2枚の独立して回転する迷路を行き来しながらタイムストーンを見つけるタイプだったなぁ。結局あの形に変更されたのは、マリオカートが出たせいｗ [Come to think of it, Sonic CD‘s Special Stages were a development of Sonic 1‘s Special Stages that took advantage of the Mega CD’s rotating function in the early stages of development, and was a type where you could find the Time Stone by going back and forth between two independently rotating mazes. After all, it was changed to that form because Mario Kart came out lol]” a popular racing game that had garnered attention for its gameplay mechanics and competitive racing experience.

Characters

Sonic CD introduced two new characters: Metal Sonic and Amy Rose. The concept for Metal Sonic was conceived by Hoshino, with a focus on creating a “menacing” character. To achieve this, the team decided to incorporate red eyes to enhance his intimidating presence. His distinctive feature, the jet engine in his chest, was a result of several ideas aimed at portraying his incredible speed. The visual design of Metal Sonic was influenced by contemporary CGI trends in the industry at that time.^[13]Sega (December 12, 2011). Sonic CD – Developer Diary. YouTube. Retrieved on August 2, 2023.

Amy Rose, on the other hand, emerged through a collaborative brainstorming process involving various team members from different departments.^[14]Stuart, Keith (November 6, 2014). Sega Mega Drive/Genesis: Collected Works. Read-Only Memory. p. 289. ISBN 978-0957576810. “Kazuyuki Hoshino: Although I created the in-game graphics for Amy, there were many people involved in the birth of the character, with staff members from various departments all contributing ideas. Just like Mickey needs Minnie to exist, Sonic’s world needed a heroine that could not be ignored. Her fashion – the headpiece and trainers – reflect Naoto Ohshima’s taste, while her mannerisms reflect the kind of traits I looked for in women at the time.” Ohshima contributed to shaping her appearance,^[15]Sonic the Hedgehog – Developer Interview Collection. Shmuplations.com. Retrieved on February 10, 2019. while Hoshino played a significant role in finalizing her design,^[16]Naoto Ohshima on Twitter. Twitter. Archived from the original on February 10, 2019. Retrieved on February 10, 2019. “Naoto Ohshima: An image of Retro Amy’s decision was found. Mr. Hoshino painted the picture. Retro Amy’s design finish^[sic] was Mr. Hoshino.”^[17]Naoto Ohshima on Twitter. Twitter. Archived from the original on February 10, 2019. Retrieved on February 10, 2019. “Naoto Ohshima: This picture is me, but Amy’s finish design^[sic] is Hoshino.” establishing her personality traits, and crafting her sprite animations.

Design and Art

Hiroyuki Kawaguchi served as the art director for Sonic CD, leading a team of five designers responsible for creating the pixel art that adorned the levels’ environments. Their task was to achieve a consistent visual aesthetic across all time zones while also ensuring each zone maintained a distinct appearance from the others. This endeavor drew inspiration from various sources, including films, books, and illustrations, notably including the influence of “Back to the Future.” The creative team explored numerous color palettes to find the most fitting choices for the different levels.

The game’s Badniks, robotic enemies, drew their design inspiration from insects such as cicadas, ladybugs, and bees. The bosses were intentionally crafted to complement the visual design of the respective stages. Despite the experimentation and diverse influences, the overall art style of Sonic CD stayed relatively close to that of Sonic 1, largely guided by Ohshima’s creative direction.

Animated Cutscenes

In response to criticisms of the “plain” endings in Sonic 1 and 2, the developers of Sonic CD aimed to create more engaging conclusions for the game. Leveraging the Sega CD’s increased storage capacity, they envisioned fully animated sequences that would captivate players and provide a more immersive experience. Thanks to the budget secured from the success of Sonic 1, they were able to turn this vision into reality. To achieve this, they collaborated with Toei Animation, a renowned studio responsible for several popular anime series at the time.

For the production of these animated cutscenes, Toei Animation enlisted the assistance of Studio Junio (later known as Junio Brain Trust). Importantly, the animators from Dragon Ball were brought in to contribute their expertise to the project at the developers’ request.

The process of creating these cutscenes involved traditional animation techniques. Characters were meticulously drawn frame by frame on paper, then traced onto transparent cels and colored. These cels were photographed against carefully crafted background art, and additional layers were incorporated to enhance visual effects. The development team played a significant role in guiding the production, ensuring that the animations aligned seamlessly with their creative vision.

When adapting the animated sequences for compatibility with the Sega CD, certain limitations had to be taken into account. The graphics still needed to pass through the Mega Drive’s video chip, which imposed constraints on factors like available colors and resolution. Additionally, the animations had to be compressed to enable real-time streaming from the CD. Despite these challenges, the inherently cartoonish style of animations in Sonic CD made them well-suited for color reduction, ensuring that the final outcome remained visually satisfactory.

Sonic CD employed the STM file format for its animations, delivering uncompressed visuals to the video display processor. This choice of format yielded superior results compared to the Cinepak compression method used in many other Sega CD titles. Notably, the game’s opening sequence alone occupied a substantial 13 MB of storage, surpassing the size of the average cartridge at the time by over eightfold. Remarkably, this opening segment was actually one of the earliest components of the game’s development to be completed.

The music for Sonic the Hedgehog CD was crafted by Naofumi Hataya and Masafumi Ogata. Notably, it marked the first entry in the Sonic series to incorporate vocal tracks, featuring vocals performed by Keito Utoku. Among these tracks, the opening song was titled “Sonic – You Can Do Anything,” while the ending song bore the name “Cosmic Eternity – Believe in Yourself.”

However, the North American release of Sonic the Hedgehog CD experienced a delay in order to introduce an entirely new soundtrack composed by Spencer Nilsen, who had previously created soundtracks for other Sega CD games. David Young also contributed to this effort. The majority of the original tracks were replaced with new compositions, with one exception being the “past” tracks. These were sequenced PCM tracks that were hard-programmed into the game, akin to other Genesis Sonic soundtracks. As such, replacing and programming new music for these tracks would have required a significantly longer amount of time. A new song called “Sonic Boom,” performed by Nilsen and the band Pastiche, was incorporated for both the opening and ending sequences of the game.

The differing soundtracks of Sonic the Hedgehog CD notably sparked a division of opinions, leading to significant debates about which version was superior. GameFan, a gaming magazine, awarded the Japanese version a perfect score of 100%, but offered a lower score for the American release, explicitly attributing the score reduction solely to the soundtrack change and not any alterations in gameplay.^[18]GameFan (2): 18. January 1994. Archived from the original. Responding to the soundtrack controversy, Spencer Nilsen expressed his view that the arguments were “ridiculous” and emphasized that both soundtracks represented distinct musical philosophies and approaches.^[19]Horowitz, Ken (December 8, 2008). Interview: Spencer Nilsen. Sega-16. Retrieved on November 16, 2021. He suggested that critics were searching for reasons to criticize the game, though he acknowledged the challenge of replacing a game’s soundtrack after it had been released for some time, likening it to changing the soundtrack of an already-released Star Wars movie.

Both the Japanese and American soundtracks of Sonic the Hedgehog CD have been featured in various music albums associated with the series, and they have also been remixed in subsequent releases. Albums such as “Sonic the Hedgehog Boom” include slightly reimagined versions of tracks from the American soundtrack. “Sonic the Hedgehog – Remix” presents original compositions by Naofumi Hataya that incorporate samples from the Japanese soundtrack. The “Sonic the Hedgehog CD Original Soundtrack 20th Anniversary Edition,” released in 2011, encompasses all tracks from the Japanese soundtrack and features remixes of “Stardust Present” and “Sonic Boom” from the American version, performed by Crush 40 and Cash Cash. Additionally, the Japanese soundtrack was released on vinyl as part of the Sonic CD vinyl album in 2019. In the Sonic the Hedgehog 30th Anniversary Symphony in 2021, Crush 40 once again performed “Sonic Boom.”

• Round Select: At the title screen, press ↑ ↓ ↓ ← → .
• View Staff’s Time Attack Records: At the title screen, press → → ↑ ↑ ↓ .
• Move Title Screen Clouds: At the title screen, hold the and press ↑ ↓ ↓ ↓ ↓ ↑. The clouds can then be controlled using on the second controller.
• Sound Test: At the title screen, press ↓ ↓ ↓ ← → .
• Edit Mode: At the sound test, select FM40, PCM12, DA11, and then press START. An image of Tails will also be displayed.
• Secret Special Stage: At the sound test, select FM#07, PCM#07, DA#07, and then press START.
• Hidden Images: At the sound test, select specific options and then press START.

Code	Image	Description	Music played	Artist
FM#44 PCM#11 DA#09		Reads: You are cool by Sanchanzu	The Palmtree Panic good future theme plays here.	Masahiro Sanpei
FM#42 PCM#04 DA#21		Parody of Batman. Reads: S O N I C THE HEDGE HOG	The final boss theme plays here.	Takumi Miyake
FM#42 PCM#03 DA#01		Reads: “The Fastest DJ” MC SONIC Can I kick it? Come in Bad boys! K.H	The Metallic Madness present theme plays here.	Kazuyuki Hoshino
FM#46 PCM#12 DA#25		Reads: Infinite fun. Sega Enterprises -Mazin Picture	The boss theme plays here.	Masato Nishimura
FM#40 PCM#12 DA#11		Tails and his favorite car, the Lotus Seven.[26]Sonic the Hedgehog 2 (Sega Mega Drive) Japanese instruction booklet, pg. 42. Also enables Edit Mode. Reads: SEE YOU NEXT GAME Judy·Totoya	The D.A. Garden Little Planet theme plays here.	Yasushi Yamaguchi

Shogakukan created a manga adaptation of Sonic the Hedgehog CD, which was included as the concluding part of the Sonic the Hedgehog manga published in the Bessatsu CoroCoro Comic Special magazine. This adaptation was serialized from December 1993 to June 1994.

In addition, the main storyline of the Sonic the Comic series spanning from issues #24 to #28 included an adaptation of Sonic the Hedgehog CD. This adaptation was incorporated as a part of the larger “The Sonic Terminator” arc within the comic series.

Archie Comics further expanded the tie-in for Sonic the Hedgehog CD by featuring it in Sonic the Hedgehog #25. This tie-in issue explained that the events of the game were situated within the alternate reality known as “In Another Time, In Another Place.” Moreover, Sonic the Hedgehog CD was also integrated into the Post-Super Genesis Wave timeline. It received an adaptation in Sonic the Hedgehog #290, which served as the concluding installment of the Sonic the Hedgehog comic series. This adaptation constituted the third part of the “Genesis of a Hero” storyline.

• The Sonic Gems Collection version of Sonic the Hedgehog CD features clear water due to being a direct port of the Windows 95 version. This version utilized a specific graphics card for water rendering, which was not emulated in the compilation.
• The “Past” background music tracks, stored in PCM format, are unable to be played in the D.A. Garden.
• Sonic the Hedgehog CD stands as the inaugural game in the Sonic series to incorporate animated cutscenes. The animated short introducing the Sega CD version of the game is notably shorter than the intro in the PC and GameCube ports, but its slower animation maintains the same duration.
• The uncut intro showcases more of Sonic traversing the landscape, including running over a lake. Interestingly, a brief segment featuring a mountainside used by Dr. Eggman to tether the Little Planet down, adorned with a large carving of Eggman’s face, is absent from the uncut intros but present in the Sega CD version. Additionally, a small segment missing from the original version’s ending FMV was restored in Sonic Jam and Sonic Gems Collection. This segment can be viewed in its original form at the Pencil Test.
• Upon entering Edit Mode in Sonic the Hedgehog CD, a hidden image of Tails becomes visible. Tails is also seen in the Tornado at the D.A. Garden/Play Music.
• In the North American instruction manual, the prologue is almost identical to its European counterpart. However, the character named Amy Rose is referred to as “Princess Sally” in the North American version, aligning with the Sonic the Hedgehog television series where Sally was the lead heroine. In later releases of Sonic the Hedgehog CD, the correct name, “Amy,” is used for the character.
• Sonic the Hedgehog CD is the first Sonic game to incorporate centiseconds in the time counter, going beyond just minutes and seconds.
• Regarding the endings, the original Japanese and European versions of the bad ending display the text “TRY AGAIN AND SAVE LITTLE PLANET FOREVER.” In contrast, the North American and Brazilian releases omit the second line, resulting in a simpler “TRY AGAIN.” This alteration is maintained in subsequent versions like the PC port and the 2011 digital release, possibly influenced by the impending release of Sonic the Hedgehog 4: Episode II. The North American version also contains other minor changes, such as allowing players to restart the level in their current time period at the cost of a life.
• In terms of character design, Metal Sonic’s in-game sprites feature white eyes and a tail, reflecting earlier concept artwork before subsequent modifications.
• Sonic the Hedgehog CD is the second Sonic game to feature voice acting, the first being SegaSonic the Hedgehog. For instance, when Sonic remains idle for three minutes, he exclaims “I’m outer here!”^[27]Masato Nishimura on Twitter (Japanese). Twitter (July 9, 2017). Retrieved on December 6, 2018. before leaping off the screen for a Game Over. Likewise, when earning an extra life, Sonic shouts “Yes!”
• In Edit Mode, there are unused sprites depicting Sonic sneezing. Additionally, an unused Item Box containing a silver ring can be added during gameplay. Breaking the monitor bestows Sonic with 50 Rings and triggers the lamppost sound effect.
• The placement of Sonic the Hedgehog CD within the series’ timeline was initially complex, as no specific chronology was established during the game’s development. Ken Balough mentioned that the game’s timeline had no official spot except occurring sometime prior to Sonic the Hedgehog 4: Episode I.
• According to Masato Nishimura, the landscape designer for the game, Sonic the Hedgehog CD’s timeline is ambiguous. Nishimura also deemed Yasushi Yamaguchi’s previous statement a contradiction, given Metal Sonic’s more advanced nature compared to Mecha Sonic.^[28]Masato Nishimura on Twitter (Japanese). Twitter (February 13, 2022). Retrieved on December 21, 2021.
• Ian Flynn confirmed that Sonic the Hedgehog CD occurs between the original Sonic the Hedgehog and Sonic the Hedgehog 2^[29]BumbleKast for February 21st, 2022 – Priority Q&A Podcast with Ian Flynn (39:15). YouTube (February 21, 2022). Retrieved on February 22, 2022. in Sonic Origins, a compilation where players experience the four Sonic games in chronological order.
• Sonic the Hedgehog CD introduced a game save feature for the first time in the Sonic series.
• Sonic the Hedgehog CD’s unique screen, exclusively seen upon completing the game with all Time Stones and low Time Attack scores, stems from its direct port from the Windows 95 version, which in turn was not emulated in the compilation.
• The European manual of Sonic the Hedgehog CD contains numerous mistranslations, especially in the Spanish paragraphs, including erroneous interpretations of “Dash Zones” and the names of specific zones. Similar mistranslations occurred in the French and Italian versions, potentially stemming from a misunderstanding of the English paragraphs.

• Sonic the Hedgehog CD at Wikipedia, the free encyclopedia