Bonus characters
Complete the indicated task in Superstars mode to unlock the character.

Alex Kidd: Complete Tournament Singles in the "Alex Kidd" stage. 
Amy Rose: Complete Tournament Singles in the "Sonic The Hedgehog" stage. 
Gilius Thunderhead: Complete Tournament Singles in the "Golden Axe" stage. 
Gum: Complete Tournament Doubles in the "Jet Set Radio" stage. 
MeeMee: Complete Tournament Singles in the "Super Monkey Ball" stage. 
Pudding: Complete Tournament Singles in the "Space Channel 5" stage. 
Reala: Complete Tournament Singles in the "NiGHTS" stage. 
Shadow the Hedgehog: Complete "Tournament Doubles" in the "Sonic The Hedgehog" stage.