On" Sonic the Hedgehog 2 with Sonic and Knuckles, you can play  Sonic the Hedgehog 2 as Knuckles the Echidna! Play as Knuckles and discover  new areas and item locations. Gather all seven Chaos Emeralds and transform  in Super Knuckles and defeat Dr. Robotnik. Go Knuckles! Go where no hedgehog  has gone before!!