Alternate costumes:
Complete one player battle mode with any character under any difficulty level.
Highlight that same fighter on the character selection screen and press Start.

Submission: Al Amaloo (vgstrategies.miningco.com)

Fight Dynasty Warriors characters:
Complete one player battle mode with any character under any difficulty level.
Highlight that same fighter on the character selection screen and press R2.

Submission: Al Amaloo (vgstrategies.miningco.com)

Random level:
Press Start at the level select screen.

Submission: Al Amaloo (vgstrategies.miningco.com)