Sparkly Kelly
Start a 1 or 2 player game and choose Kelly as your character. When the match starts perform your attack, and hit start as she winds up to deliver it. choose "retry" from the pause menu and when the match restarts, Kelly will be surrounded by sparks which will last for the remainder of the match, or until she performs another attack.
Flat Characters
Pick either Burger Dog or Hamm as your character. When you're "grooving" do your special attack twice in a row.
Alternate character color
Highlight a character, then hold Select and press X.
Play as Capeiora
To get Capieora, beat the game on NORMAL difficulty with any character.
Play as Columbo
To play as Columbo, beat the game on NORMAL with Shorty.
Play as Robo-Z
To get Robo-Z, beat the game with anyone on HARD.
Play as the Burger Dog
First get Capoeira and Robo-Z then beat the game on Normal with Hamm. Scroll down/off the player select screen until you get Burger Dog. His moves are the same as Hamms.
Zoom Winning Poses
When you win the stage, hold the CIRCLE button to zoom in on your character.
Play as alternate character
At the character selection screen, highlight a character, then hold Select and press Circle.
Level skip
Beat the game once with any character. Then, start a game in single player mode and when a song begins, press L2 + Select to jump to the next level.
Dance preview
Beat the game on the easy difficulty level.