|Buster's Lanes Level|
Kill 20 guys in endurance mode to unlock the Buster's Lanes level.
|Holiday Havoc Level|
Kill 30 guys in endurance mode to unlock the Holiday Havoc level.
|Play As Axel|
In the Playground Peril level in tournament mode, shoot a missile at the middle swing on the swing set that is in the background next to the merry-go-round. A small statue of Axel will be thrown into the playing area. Pick that up to unlock Axel.
|Play As Darkside|
In the Kitchen level, go to the sink and drive down the plumber's butt. Go onto his leg and napalm his butt. He will blow a hole in the wall. Enter the hole to unlock Darkside.
|Play As Mime|
In the Holiday Havoc level in endurance mode, shoot missiles at the Christmas tree until it is destroyed. Get on top of the fireplace then jump off backwards and shoot a missile at the stockings. Destroy all four to reveal the icon that unlocks Mime.
|Play As Trapper|
Successfully complete the game with Mime to unlock Trapper as a playable character.
|Shock Therapy Level|
Kill 10 guys in endurance mode to unlock the Shock Therapy level.
- Freeze: Press Up, Down, Up.
- Shield: Press Right(2), Down(2).
- Rear Fire: Press Left, Right, Down, L2.
- Drop Mine: Press Right, Left, Down.
- Jump: Press L1 + R1.