Secret boxers:
In Open Style, fight until you are champion to access a 
Jack-In-The-Box boxer. Defend the championship title five 
times to access Snake. 

In Peek-A-Boo, fight until you are champion to access Kiki and 
Mimi. Defend the championship title five times to access 
Edward King (the promoter). 

In Peek-A-Boo, fight until you are champion to access Roboxer. 
Defend the championship title five times to access Carrie (the girl 
that carries the round cards).