To play as both Ravage and Tigatron, highlight Cheetor at the character select screen and press Z and A. Then move left or right to select the other to characters.

To play as Starscream, highlight Waspinator at the character select screen and hit Z and A. The move left or right to select Starscream.

To play as Blackarachnia, highlight Tarantulas at the character select screen and press Z and A. Then move left or right to select the new character.

To unlock Ravage in Arcade or Versus Mode, at the Character Select screen, stop on Cheetor, Hold the Z Button and press A. Now, Use the Left and Right to cycle through the color selections until you see Ravage.