Aww, I love Captain Underpants. The books are kind of young, but I can almost see it turning into a cartoon.
What about Ed from "Ed, Edd and Eddy?"
Ed Edd 'n' Eddy has a lot of lolcows, actually.
All three of the Eds count, but Eddy is the biggest lolcow of the three. He's a loudmouthed asshole who obsesses over scamming the other kids out of their money so they can buy jawbreakers at the candy store. Double D is an obsessive-compulsive neat freak who labels literally
everything in his room and freaks out if something isn't
exactly in its place. Ed is a full-on exceptional individual who is literally a basement dweller. His room makes Chris's look clean in comparison.
Jonny 2x4 is a weird loner whose best (and pretty much only) friend is a piece of wood with a face drawn onto it in crayon named "Plank." He treats Plank as if he were real, and has even made parents for him. When the Eds accidentally break said "parents" in half, Jonny acts as though they were real people who have been murdered. He also has his own super identity called "Captain Melonhead," similar to Chris's many alter egos.
Rolf is an immigrant who seems to come from an entire country of lolcows. In the episode where the Eds make him think that he's back in his old country, it is revealed that they do things such as balance themselves onto poles to buy and sell things, pay for stuff with chickens, and hold village idiots in high regard. They also have folk songs that people are meant to beat each other up to. That's not even getting into all the strange idioms and stories Rolf uses throughout the series.
Sarah is a spoiled brat who physically abuses her brother (Ed) and spergs out whenever she doesn't get her way. Her best friend Jimmy is an effeminate boy who reacts to a clothespin tapping his foot as though he broke his foot. Though, to his credit, he's also shown to be really smart and cunning when the situation calls for it.
The Kanker Sisters are horrorcows, as
@DirkBloodStormKing said. They are obsessed with the Eds, whom they consider to be their boyfriends, and routinely attempt to kiss them (and possibly more; there's a lot that isn't shown). They come from a white trash background, and each of them has their own dad (who presumably left their mother, a man-hater). They are also extremely petty and destructive. In one episode, they literally destroy the entire cul-de-sac once their ship-in-a-bottle goes missing.
Eddy's brother, who is absent for the entire series and only appears in the last ten minutes or so of the movie, can be inferred to be a lolcow/horrorcow. He's an adult man who still acts like a teenager and physically abuses Eddy. From what little we see of him, it's likely that he'd fit in rather well with Deagle Nation, seeing as how he's got the overgrown teenager part down pretty well.