Speed up Game play
At the Selection screen, press:
Fast - DOWN + MP or MK
Faster - DOWN + FP or PK
Fastest - Hold UP, press FP, MK, QP

Gargos Code
During any Character Demo, press Z, A, R, Z, A, and B. When done correctly, you will hear a laugh. Select Arcade Mode.

Multi-Colored Players
During an Character Demo, press Z, B, A, Z, A, and L. When done correctly, you'll hear, "Welcome."

Sky Level
Go to the Character Select screen in two-player mode. Have both players select their player by holding DOWN + MK (or C-Down), just as if they were selecting a stage/music. You can now play in the sky.

View Credits
To view the credits without finishing the game, press Z, L, A, Z, A, and R.

Options Menu (Instantly)
Push Z, B, A, L, A, and Z. If done correctly, you will, "Perfect."