There are a few unused songs found within the game's data. One is an alternate version of the character select screen (which is used in the options menu in the Sonic Gems Collection port), one is called "Sunset Town" on the official OST yet doesn't make an appearance in the actual game, another is unused and is not found in the OST so it is impossible to tell what it may have been used for, and the final track is named "Hurry Up". Based on the name it sounds like it could have been used for the Death Egg Hanger, but this track goes unused anyway. Strangely enough, this song became the pre-race cinematic music in the Death Egg DLC for Sonic & All-Stars Racing Transformed.
Contributed by SonicManEXE
Dr. Robotnik's name is misspelled in the intro as "Dr. Robotonic".
Contributed by SonicManEXE
Honey the Cat is based on Honey (AKA Candy) from the game Fighting Vipers. She was planned for the original arcade release of the game, but was eventually scrapped. However, she was later reinserted into the HD remake of the game.
Contributed by Funland47