Unlock all Prisons (only unlocks Prize Fighter in Alpha Star Complex): In the Prison select screen:

PlayStation: Hold [Select] and press [R1], [R2], [R1], [L1], [R1], [L2], [R1], [R1], [R2], [R1], [L1], [L1], [R1], [L2], [R1]

Dreamcast: Hold [LT] and press [A], [B], [A], [X], [A], [Y], [A], [A], [B], [A], [X], [X], [A], [Y], [A]

Unlock Bonus Facility: In the Prison select screen:

PlayStation: Hold [Select] and press [R1], [R1], [R1], [R2], [R1], [L1], [L1], [L1], [L1], [R2], [R1], [L1], [L1], [L2]

Dreamcast: Hold [LT] and press [A], [A], [A], [B], [A], [X], [X], [X], [B], [A], [X], [X], [Y]

Unlock The Doctor: In the Character select screen:

PlayStation: Hold [Select] and press [R1], [R1], [R2], [L2], [L1], [R2], [L2], [R1], [L1], [R2], [R2], [L1]

Dreamcast: Hold [LT] and press [A], [A], [B], [Y], [X], [B], [Y], [A], [X], [B], [B], [X]

Enter Bouncy Mode: In the Arena select screen:

PlayStation: Hold [Select] and press [R1], [R2], [L1], [L1], [R1], [R1], [R2], [L1], [L2], [R2], [R2]

Enter Slippery Mode: In the Arena select screen:

Playstation: Hold [Select] and press [R2], [L1], [R2], [R1], [R2], [R1], [L1], [L2], [L1], [R1], [L1], [R1], [R2], [R1], [R2], [L2]