Knuckles the Echidna is a video game character and a hero of the Sonic The Hedgehog game series, as well as some spin-off games and comics. His first appearance was Sonic the Hedgehog 3, released in 1994 to introduce a new rival for Sonic, presented as an antagonist who was tricked by Dr. Eggman into fighting Sonic. Knuckles is a 16 year old red anthropomorphic echidna, who is both physically powerful and highly resilient. He has a white crescent on his chest and four knuckles, two on each hand, which are actually sharp spikes. He is both a friend and a rival to Sonic.
During conception of Sonic the Hedgehog 3, the development team wanted to create a new rival for Sonic. The final design of Knuckles was the result of dozens of possible designs inspired by numerous different animals. The emphasis of the character was to break walls.
Ever since the character appeared in Sonic the Hedgehog 3, he has been thought of as an “intimidator” because of his powerful abilities. The character was given a headlining role in the next game, Sonic & Knuckles.