Baby Boomer

To earn some extra lives, perform any of the following actions.

Level 1: Repeatedly shoot at the fire hydrant.
Level 2: Repeatedly shoot the thin, tall tombstone.
Level 4: Repeatedly shoot the stalactite over the bridge.
Level 6: Repeatedly shoot the torch

During gameplay, hold Up and A, then press B on Player 1's controller. Then you can hold B and press Select to skip the levels - there are ten in all made available to you. (Going above Level 10 loops you back to Level 1.)