Link mode
Hold down [Select] and press [Up], [Down], [Left], [Right], [Down], [Up] at the options menu . The "Players 1 or 2" option will be unlocked, which allows the two player mode to be played on two Game Boy Color systems using a link cable.
Play as Tiny
Select Ralph as a character, then intentionally die. Then, quickly press "Select, A, B"(2), "Up, Down, Forward, Back" after transforming into a person.