Balloon Heads
At the wrestler select screen press L1 seven times then L2+select and you should hear a wacky sound during the match as the wrestler takes damage his head will get bigger and bigger.
Unlock all wrestlers:
At the character select screen press R1, R1, R1,R1, L1, L1,L1, L1, L1, R2,
R2, R2, R2, L2, L2,
L2, L2, select.
New Rings:
At the options screen scroll down to the rings. Then hit R1, R2, R1, R2,
select. Then every time you hit select your ring will change. You will get new rings.