The Grim Adventures Of Billy And Mandy

Concept art:
Hold Circle and press Up(2), Down(2), Left, Right, Left, Right at the main menu.

Play as Boogey:
Successfully complete Mission 9 in Tier 4 in Mission mode.

Play as Chicken:
Successfully complete Story mode as all characters and accumulate 10 hours of game play.

Play as Clown:
Get 200,000 damage points and play over 100 verses battles.
UR50SLO.

Play as Dracula:
Successfully complete Mission 5 in Tier 3 in Mission mode.

Play as Eris:
Successfully complete Story mode as Billy, Mandy, Grim, or Irwin.

Play as Fred Fredburger:
Successfully complete Story mode as Billy, Mandy, Grim, or Irwin

Play as General Skarr:
Successfully complete Mission 6 in Tier 4 in Mission mode.

Play as Hoss Delgado:
Successfully complete Mission 9 in Tier 1 in Mission mode.
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Play as Jack O'Lantern:
Successfully complete Mission 9 in Tier 2 in Mission mode.

Play as Lord Pain:
Successfully complete Mission 9 in Tier 5 in Mission mode.

Play as Mogar:
Successfully complete Story mode as Billy, Mandy, Grim, or Irwin.

Play as Nergal Jr.:
Successfully complete Mission 9 in Tier 3 in Mission mode.

Play as Nergal:
Successfully complete Story mode as Billy, Mandy, Grim, or Irwin.

Play as Nerglings:
Successfully complete Story mode as all characters.

Play as Pumpkin:
Successfully complete Story mode as all characters and deal out a total of 100,000 damage points.
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Play as Vikings:
Successfully complete Story mode as all characters and destroy every letter in the credits sequence.

Alternate costumes:
Successfully complete Story mode with any character to unlock an alternate costume for that person.

When you complete Story mode with a character that has a costume and you destroy the credits, Mandy will be in a costume.
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To unlock a second set of costumes, successfully complete all fifteen Mission mode matches.