MARVEL VS. CAPCOM UNLOCKABLES
Unlock Red Ryu (Ken)
Press Down, Down/Back, Back, Medium Punch. You must have at least level 1 on you hyper combo bar, and can be done in easy mode.
Change back to normal Ryu
Press Down, Down/Back, Back, Quick Punch. You must have at least level 1 on you hyper combo bar, and can be done in easy mode.
Full pause screen
Press Start to pause your game, then hold Y and press X.
Alternate costumes
Highlight a fighter, then press A or Y at the character select screen.