In cartoons, a character is easily inflated with a bicycle pump so that his muscles fill out and he gets bigger a until he pops. Ever wonder what that looks like in real life?
Well, then you'll be a huge fan of "muscle morph" a YouTube genre where users take current pictures and fill the guys bodies out so that they're bigger and beefier than before. Usually it involves a 98-pound weakling turned into a muscle god or someone who looks like a body builder and turning him into a lumpy Incredible Hulk.
We've seen it with famous people, unknowns, and everyone in between. Much like the whole plushie/furry fetish, we bet this actually has something to do with inflation in cartoons coupled with the animated beefcake like He-Man and Superman.