Unlock All Wrestlers:
Select "Edit Wrestler", then choose the "Name Entry" option. Enter "ALL" for "Nickname", "STYLE" for "First Name", and "CLEAR" for "Last Name". Then, set "Exchange" to "Off", "Middle" to "Space" (Square icon), and press Start. Press B until you return to the main menu. All wrestlers will now be unlocked.

GameShark Codes

Freeze Round Timer  
094BF7579070F70E  

Master Code   
FD330A9D7A163079
BF7A819985CE4412
 

Thanks to Revolution reader Golden Midge!