Oh man! It's-a Sweet Cuppin' Cakes!
Surreal cartoon world posited by Strong Bad in his 72nd email, "crazy cartoon". It's Strong Bad's idea of a "kah-razy cartoon".
The main character is "a mix between a cow and a helicopter" - a splotched blue blob with yellow legs who hovers around making "just these weird sounds with no words" and chasing a worm who pops from a hole in the linoleum from time to time. The worm is a cross-hatched ink drawing in a world of full-color vector dudes, which is crazy!!
Eh! Steve doesn't need these lowbrows. He's a sharp, savvy quadrilateral sporting a handlebar mustache and stubby limbs. He exists to deliver his eponymous line and to flee from his mortal enemy - the Wheelchair, a sketchy guy voiced by Bubs. "I know you're out there somewhere, Eh! Steve! I'll blast you till tomorrow noon!"
Strong Bad also narcissistically adds a version of himself with Casio keyboard in place of head. When angered, he plays the demo song and dances.
SCC characters have a bit part in email #84, "kids' book". (We learn that "Eh! Steve is not exactly a person.") It's also the theme of a menu on Homestar Runner's website. Finally, the cartoon's theme song made the Strong Bad Sings LP, and it best sums up the beautiful philosophy underlying all things Sweet and Cuppin':
Everybody knows it, everybody knows it, everybody knows it, everybody knows it -
Watch out for Eh! Steve!