Sonic the Hedgehog (OVA) was the first Japanese anime adaptation of the Sonic the Hedgehog franchise and was originally released May 16th, 1996 as a two episode series. ADV Films would then later acquire the series’ license, dub it in English and release the series as a movie on September 9th, 1999; which incidentally was also the same day that both the Dreamcast and Sonic Adventure were released.
Sonic the Hedgehog takes place on the planet Freedom where we find Sonic and Tails having a relaxing day at the beach, when all of a sudden the President’s steward, Old Man (Old Owl), comes crashing towards the earth. After a failed attempt by Tails to save Old Man, Sonic manages to rescue the two of them from being impaled on the side of a cliff; and finds out that the President wants both Sonic and Tails to come to the Presidential Palace right away. Once there, the duo discover that Dr. Robotnik has captured both the President and his daughter, Sarah, in order to get Sonic to destroy a giant mech, known as Metal Robotnik (Black Eggman), which has taken over Robotropolis and stop the jammed robot generator from causing a giant explosion. Little does Sonic know that it’s all an elaborate trap, set by Dr. Robotnik in order to activate Hyper Metal Sonic and destroy Sonic once and for all.
During the translation by ADV, the two regions that cover planet freedom are referred to as being separate dimensions. This is often referred to as an error in translation. However, if the word is taken in its literal sense, a dimension is simply the property of space that is formed by the body that occupies it. Taking this into account, the “Land of Darkness,” being the actual surface can be considered one dimension; while the “Land of the Sky,” which forms a shell like structure around the planet, connected by an ice formation, can be considered another dimension. This doesn’t mean that you can simply walk, fly or dig your way to either dimension. In order to access a dimension, one must travel through a super-cell hurricane-like vortex that acts like a portal or by using one warp-zones that are scattered all over planet Freedom.
Once Sonic and Tails reach Robotropolis (Eggmanland), they find a post-apocalyptic city covered in vines and sinking into the sea. The city itself was most likely inspired by Manhattan as seen by its iconic landmarks, such as the Chrysler Building and they city’s skyline.
The only censorship that’s still found in the ADV Film version is the few curse words that are said in the Japanese version by Sonic and Knuckles, but are translated as “Oh no!”