Knuckles the Echidna

Knuckles the Echidna is a close friend of Sonic the Hedgehog. Like Buzz Lightyear, Taz, and Patrick Star, he's "dumb" and childish. Hence his name, he is a knucklehead.

The first appearance of Knuckles the Echidna in Woody and Daffy Duck Surviving Five nights at Freddy's 2

In Woody and Daffy Duck Watches Danny Phantom, it is revealed that he was abandoned by his mother as a child and he never had a proper education, which could explain why he's the knucklehead he is.