Sonic & Knuckles is a game/expansion released on the Sega Genesis starring Sonic the Hedgehog and Knuckles the Echidna. It is the first game to feature Knuckles as a playable character. Its success led to Knuckles becoming a playable character in Sonic the Hedgehog 3. It has since been ported to the GameCube, DS, and Virtual Console. If the player downloads both Sonic and Knuckles and Sonic 2 or Sonic 3 onto the Wii, Knuckles will become a playable character in Sonic 2 and Sonic 3.