Interesting comparison- Bloo and Dennis.
Dennis is usually trying to
help, but doesn't think everything through, and ends up being more of a pain than anything else. Bloo I think wants to help a lot of the time, too, but his ego gets in the way. So he comes across as a jerk instead.
Dennis is naive and ignorant about the goings-on of his friends, family, and his neighbors the Wilsons. Just like you'd expect a kid his age to be. That is, a very preoccupied kid with a constant flow of distractions and too many interests to count. Bloo I think is more observant than that, but wanting attention, pretends to be ignorant in the matter more than not.
Like I remember saying before, I think our dear goofy little friend Blooregard just thinks on a different dimension than everyone else, so he's easily misunderstood, both by the rest of the characters, and the also the viewers. Yeah, sometimes he's totally selfish and a big insensitive jerkface, but most of the time, I think he just doesn't know that what he's trying to do isn't going to work out the way he expects it to. His little blue brain just works differently, and he doesn't think on the same level as everyone else. Not to say he's impaired. Maybe it's the opposite. Blooregard might be a level or two above everyone else! Ha, there's a thought!
Whereas Dennis is just a normal curious, imaginative, distracted little boy. Well, maybe a little more so than
normal, but still.
As for who's worse behaved, hmmmmm..... Both Bloo and Dennis have done significant property damage. Also caused personal injuries. "Accidentally" stolen stuff. Has Dennis told fibs? He seems to be an honest boy if I remember the comic (and movie) correctly. Dennis isn't the type to want to be the center of attention and will cause all sorts of trouble to get it, either. In that case, maybe Bloo is worse behaved. Bad Bloo, Bad!! Ah, but we can't help but love you anyway!
