Knuckles the Echidna

Originally introduced in Sonic 3 Knuckles is the hotheaded Guardian of the Master Emerald and Angel Island. He is initially tricked by Eggman to think that Sonic and Tails are out to steal the Master Emerald. So as soon as they set foot on the island, he grabs the Chaos Emeralds and runs away. He constantly torments Sonic throughout the rest of the game, until he learns that Eggman is not who he seems.