So I posted something up in the BE section (my first post, after having visited this site since it was process.cc and all of that) and I've yet to see this. It could be considered classic Weight Gain, so here goes.
It's on a cartoon of Betty Boop's called "Betty Boop and Little Jimmy". Not too long on time either. Short story even shorter, she hooks herself up to a fat shaking machine (I can't think of a name for it) and she shakes herself thin. Rail thin, like Paris's friend thin. After she finally gets out of that thing. She sees how ridiculous she looks and she starts laughing. Somehow, this adds to fat. She laughs herself fat, she gets plump too. Anywho, here's the link.
The expansion starts at about 4:56.
And for some reason. despite how thin or thick she gets, her head stays as large as it always is.