Here are hidden features for Totally Rad, one is a level select/sound test and the other is a credits scroller on the titlescreen.
To access the level select and sound test you have to do the following...
On controller 1 press UP, UP, DOWN, DOWN, LEFT, LEFT, RIGHT, RIGHT, START
To access the credits scroller you have to do the following...
On controller 2 press RIGHT, LEFT, LEFT, UP, DOWN, DOWN, UP
On controller 1 press START