Knuckles the Echidna is one of the main characters of the Sonic the Hedgehog series. When he first appeared, he was tricked by Eggman into fighting Sonic. Eggman told him that Sonic wanted to steal Knuckles' Master Emerald, when he only came to stop Eggman.
Knuckles generally gets involved when his Master Emerald is in danger. He is a skilled martial artist who is just as strong as Sonic is fast. Despite her rivalry with Knuckles, Rouge the Bat has a crush on him.