Welcome to Cheatology, Gamer. You'll never know defeat again!

Gohan  Beat the game under any difficulty setting to unlock Gohan's hidden forms. 
Vegeta  Beat the game under any difficulty setting to unlock Vegeta's hidden forms. 
Goku  Beat the game under any difficulty setting to unlock Goku's hidden forms. 
Trunks  Beat the game under any difficulty setting to unlock Trunks's hidden forms. 
Broly  Beat the game under any difficulty setting to unlock Broly's hidden forms. 
Bardock  Beat the game under any difficulty setting to unlock Bardock's hidden forms. 
Krillin  Beat the game under any difficulty setting to unlock Krillin's hidden forms. 
Tien  Beat the game under any difficulty setting to unlock Tien's hidden forms. 
Yamcha  Beat the game under any difficulty setting to unlock Yamcha's hidden forms.