Press start when you catch your first Ring Girl,
while in pause hit x, o, x, o (hugs and kisses I think this works... if you figure out why sometimes it doesn't and then update me on the way to get each girl in their own round (and at least 12 skins, which I'm sure we can modify with future codes), that would be sweett.
To unlock the following fighters you must first go to "Career" mode and go to "Create Boxer". Next enter one of the following names and hometowns:
LLCOOLJ BRONX LL Cool J
HUGHEY PMANSION Hugh Hefner
MJ CHICAGO Micheal Jordan
PDIDDY NYC P. Diddy
HALLE HOLLYWOOD Halle Berry