Unlock Hidden Wrestlers
Beat the Tournament Mode with any wrestler on Normal or Hard and you will unlock a hidden wrestler. Each character will unlock a different wrestler, so try beating the game with everyone for the maximum lineup.
Unlock All Wrestlers
At the title screen, press C-Right 4 times, C-Left 4 times, the R button 4 times, the L button 4 times, and then Z. Then at the character select go to the top row of wrestlers and press UP. Repeat this process over and over until you get back to the screen with the original wrestlers.
At the title screen, press C-Left seven times, then press L, Z. This will cause the wrestler's heads to sweel with each hit. A tone will confirm the code.
At the options screen, press C-Right, R, C-Right, R, Z. From now on, every time Z is pressed, the current ring will advance to the next in the series. To move in reverse, press C-Left, L, C-Left, L then press Z until you reach the desired level.
Press B + C-Left at any time while on the Disco stage to make your wrestlers do the Y.M.C.A.!
Call For Backup
Press the Z button at any time during the match to cause a run-in to occur.
Big Heads, Hands and Feet
At the title screen, press R seven times, then press C-Right, Z. A tone will confirm the code.
Big Head Mode
At the title screen, press C-Right(7), R, Z. If you entered the code correctly, you will hear a sound. A tone will confirm the code.
At the mode selection screen, press L seven times then press C-Left 17 times. A tone will confirm the code.
All Secret Characters - Method 2
While at the screen where it says "Start" or "Options" press:
C-Right, C-Right, C-Right, C-Right, C-Left, C-Left, C-Left, C-Left, R, R, R, R, L, L, L, L, Z. If the code was entered correctly you will hear Macho Man say, "Oh Yeah"
At the title screen press C-Left, L, C-Right, R, Z. A sound will confirm a correct code entry. The new rings include Graveyard, Spaceship, Circus, Hive, Turbo, Wunderland, Boudoir, Hall of Mirrors, Rec Room (this is my favorite! you get to wrestle on a pool table!), Psychodelic, Disco, Jungle, 1984, Quark, and Texas.