* 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.
* MilestoneCelebration: Coincides with the 10th anniversary of the original game. As such, collecting 180 emblems will [[spoiler: unlock a 3D version of Green Hill Zone.]]
* 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.
* SequelFirst: ''Sonic Adventure 2 Battle'' was released first on the GameCube a year before ''VideoGame/SonicAdventure DX Director's Cut'' was released.
* UrbanLegendOfZelda: There was once a widespread rumor that Chao apparently couldn't reincarnate more than two times. It's possible for them to reincarnate potentially 255 times due to data limitations.
** While it didn't directly spawn the once-common rumor of a "Sonic and Knuckles RPG", there was some speculation that said (ultimately theoretical) project had been retooled into this game.
* 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 the Black Market was going to be in Sonic Adventure 2, instead of Battle.
*** In addition, there was a Chao Playground and Chao Library planned. The Library would allow you to create new files for the Chao Adventure VMU game, but the Playground's function is unknown. Geometry data for them still exists in the PC version.
** In ''Battle'', after getting an A-Rank on [[spoiler: Green Hill Zone, Super Shadow and Super Sonic]] would have been unlocked in two-player mode. All that exists are the unlock message and character select descriptions.