Kill 25 Mayo enemies
Collect 25 lives
Use a Guitar weapon
Complete stage 7
Complete stage 6
Defeat robot boss in stage 6
Lose 25 lives
Complete stage 5/defeat Skinny Chestknee
Complete Stage 4-2/defeat Metal Jesus Rocks
Earn enough energy points in minigame to earn a 1up
Complete stage 4
Use a Grey Alien Arm weapon
Complete stage 3
Defeat bouncers in stage 3
Complete mini-game
Complete stage 2
Defeat Big Blue Alien miniboss
Beat a boss with max health
Activate a level password
Defeat 25 aliens
Earn an extra life from high score
Defeat 25 enemies
Complete stage 1
Complete game with Ashley
Complete game with Nick
Complete game in co-op mode
Complete stage 8
Complete stage 9/defeat Darth B.
Complete stage 10/defeat Overlord
Activate a cheat code
Collect 25 invincibility powerups
Collect 25 extra attack powerups
Complete game on Metal difficulty
Complete game on Death Metal difficulty
Complete Death Metal difficulty under 1 hour 15 minutes
Complete Death Metal difficulty under 1 hour 30 minutes
Complete Stage 8-2/defeat Alpha Omega Sin
Complete Stage 11
Complete Stage 11-2/defeat Gibletor again
Complete Stage 12
Complete Stage 13
Complete Stage 13-2/defeat Metal Head boss
Complete Stage 14
Complete Stage 14-2/defeat Harvester
Make Metal Head Boss spawn 5 sets of enemies/play complete song within a single fight