At the team select screen, go create a custom player and put these names on the custom player menu. Left mouse click the DONE button twice to unlock that character.

LEMON BOY - Thor Herring
BARRY DEJAY - Barry Dejay (duh!)
KOBE - Kobe Bryant
SHAQ - Shaquille O'Neal
VINCE - Vince Carter
MJ - Michael Jordan
ALLEN IVERSON - Allen Iverson