Fight a Blarney clone -
Use a text editor to edit the "xpr.ini" file. Add the line "Player2=Blarney" to 
fight a Barney clone. Start the game and choose free play mode. 

Cheats -
Type one of the codes below at the mentioned screen.

Code - Screen - Effect
bishop - Fight - "You suck" announcement 
blood - Fight - Increase blood during fight 
glassjaw - Fight - Stun either fighter with hit 
helium - Fight - Low gravity 
invisible - Fight - Invisible fighters 
orchid - Fight - Selena blossoms 
shadows - Fight - Shadow fighting 
stain - Fight - Blood stains on ground 
thoughtjinx - Fight - Kill both fighters 
champs - Menu - Select Bosses in free play mode 
xacman - Menu - Xacman mini-game