Press [Jab] to select the current version of one of the following characters in Classic Arcade mode. Then, one enter the corresponding code as the airplane flies to the top of the screen and press [Jab] again. A sound will confirm correct code entry. The classic versions do not have super combos and and cannot reduce throw damage.

Classic Chun-Li: Press Down(3), Up.
Classic Dee Jay: Press Down(2), Up(2).
Classic Bison: Press Down, Up(2), Down.
Classic Dhalsim: Press Down, Up(3).
Classic Ken: Press Left(3), Right.
Classic Fei Long: Press Left(2), Right(2).
Classic Vega: Press Left, Right(2), Left.
Classic Blanka: Press Left, Right(3).
Classic Blanka: Press Left, Right(3).
Classic Zangief: Press Left, Right(3).
Classic Balrog: Press Right, Left(2), Right.
Classic T. Hawk: Press Right(2), Left(2).
Classic Ryu: Press Right(3), Left.
Classic Guile: Press Up, Down(3).
Classic Sagat: Press Up, Down(3), Up.
Classic Cammy: Press Up(2), Down(2).
Classic Honda: Press Up(3), Down.

To fight as Classic Akuma in Classic Arcade mode, highlight the following characters at the selection screen for about three seconds before moving on to the next person: Ryu, T. Hawk, Guile, Cammy, then Ryu again. Then, press Start + [LP] + [MP] + [HP]. In Classic Arcade-Versus/Training mode, highlight Ryu at the selection, the random character box next to Guile, Guile, Sagat, then Ryu again. Then, press Start + [LP] + [MP] + [HP].