As a kid I never knew why Betty Boop looked the way that she did, a very human body, and yet an alien like head. The reason is that she was originally a female dog, developed to interact with a cartoon dog named Bimbo. Over time she became more human like, but still had a (for lack of a better term) dog-like face, and yet was considered to be the embodiment of attraction.
Like Betty Boop, a lot of cartoon characters' mysterious features are explained by looking back at the early concepts from the artists. Mickey Mouse wears shoes to make it easier to draw for the animators. The Simpsons are yellow with blue hair because Matt Greoning wanted people to think the saturation on their televisions was off. Super Mario has a mustache because the artists couldnt draw a mouth in the small pixel image they had.
At first glance, Betty Boop, and other characters with exagerated body parts seem reasonably logical, but when you actually think about the body structure and gravity, you notice just how messed up their anatomy really is. I came across a site that has images of the skeletons of famous cartoon characters showing how their bone structure gives them their unique shape. This site can also be used to scar children for life.