While at the options screen type in this password "WWF RULES!!!" make sure there are three exclamation points or it won't work.
Or if you want to unlock indivisual wrestlers then type these in.

Hurricane Helms: Stand back!
Lance Storm: Serious!
Mighy Molly: Golly Gosh!
Shane Mcmahon: Which way!
Stephanie Mcmahon-Helmsley: No!
Kurt Angle: It's true!
D.D.P: BANG!