In the character select screen, rapidly do this combination: up, up, up, up, down, down, down, left, left, right. If done correctly, Abubo will appear in the middle of all characters.
Play as Johann
In versus mode, after you have selected your characters, hold all the buttons (ABCD) until the round starts. NOTE: Johann will mimic the colors of the character you selected, so anything other than the default color will result in a nasty appearance.