Good ****ing God, was this film awful. It tries to do a real world/western animation blend a la Who Framed Roger Rabbit?, but Roger Rabbit understand most amalgam conventions; scale, proportion, "uncanny valley"-ness, whereas Cool World is very amatuerish in how it pulls this off, and it never comes close to looking right. Aside from that, the cartoons themselves are just incredibly random and wacky. It's headache-inducing, it's tiring, but it is certainly not funny or entertaining.
The pacing is horrible, with the film taking far too long to actually start the plot. The plot itself is also fairly unfocused, and whoever thought of the mere inkling of an idea that cartoons should be allowed to have sex with humans, and that this will cause an "explosive" climax (that's literally what happens when he hits the climax) needs to stay away from writing films for the rest of his life. Did I mention that the cartoons are ridiculously wacky, annoying and headache-inducing.
Don't watch this movie.