In the Japanese version of the game "Air Combos" are referred to as "Aerial Raves". There is a sound file in the international versions of the game of the announcer saying "Aerial Rave!", which goes unused due to the change.
The Japanese Dreamcast version of the game featured an online mode, allowing players to fight each other via the Dreamcast's modem or broadband adapter. This mode was removed from the international release for unknown reasons, with the game's logo taking it's place on the menu. The music associated with the mode is still in the files of the PAL and US release, but goes unused.
The character of SonSon is in fact the granddaughter of the protagonist from Capcom's Arcade game, SonSon.
If you kill the final character of a team with Dan's Premium Sign attack as it's thrown, it will count as a Hyper Combo Finish.
According to Yoshinori Ono, the character Ruby Heart started out as a character of the Darkstalkers series before being rejected and moved over to Marvel vs Capcom.