Unlockable: Characters:
To unlock extra characters, complete the requirements and buy them from the Costumes area of the collection screen.
Peter: Beat the "Decisions, Decisions" Scenario on Hard Mode.
Greg: Beat the "Decisions, Decisions" Scenario on Very Hard Mode.
Fireman: Beat the "Hellfire" Scenario.
Frank: Beat the "Decisions, Decisions" Scenario with George.
Monica: Beat the "Below Freezing Point" Scenario with Yoko.
Yoko D: Beat "Outbreak" with Yoko.
Bob: Beat "Outbreak" with Mark.
Will: Beat "Outbreak" on Very Hard Mode.
Unlockable: Hard Mode:
Beat all Scenarios once.
Unlockable: Infinite Ammo:
To make the infinite ammo mode purchasable in the shop, get 100% completion in all scenarios.
Unlockable: No Partner Mode:
Beat all Scenarios once in Hard Mode.
Unlockable: Very Hard Mode:
Beat all Scenarios once in Hard Mode.