* HeyItsThatVoice: Rouge the Bat is voiced in English by Creator/LaniMinella, who did voicework in [[VideoGame/SonicAdventure the previous game]] as the female PA in Station Square and Twinkle Park.
* TheOtherDarrin: Knuckles is voiced by Scott Dreier in this game, when he was voiced by Michael [=McGaharn=] in the first. However, their voices are similar enough, so it's hard to notice the change.
** Tails, who was voiced by Corey Bringas in the first game, is now played by Corey's younger brother, Connor.
* WhatCouldHaveBeen: Originally the game was only going to feature Sonic, Knuckles, and Eggman as playable characters. The alternate stages would be branching, a feature that would return in Shadow the Hedgehog.
** Shadow’s original name was “Terios”, which means, “reflection of”, and Rouge’s original name was “Nails”
** Sonic was originally going to wear his sneakers from the Genesis games, instead of his SOAP shoes which enabled him to grind.
** [[http://www.sonic-cult.org/dispart.php?catid=3&gameid=5&subid=2&artid=5 Some leftover data]] from the Dreamcast version shows that originally Chao Kindergarden was going to be in Sonic Adventure 2, instead of Battle.