MDK 2: Armeggedon
Begin game play as Max, then hold R2 and press Up(4).
Kurt in boxer shorts:
Hold L2 + R2 and press Square(2), Triangle, Square at the main menu.
Pause game play, then hold L2 + R2 and press Up, Down, Right, Left, X, Triangle, Circle, Square, Square + Start to play as a character that is part Kurt, Max, and Doctor Hawkins.
Pause game play, then hold L2 + R2 and press Circle, X, Circle, X.
Crazy camera views:
Pause game play, then hold L2 + R2 and press X, Circle, X, Circle.
Fart sounds from Doctor Hawkins:
Begin game play as Doctor Hawkins, then press L2 + R2 + Left + X.