Children will mock anything really, from kids in wheelchairs to lisps to even burn victims. Adults are generally more accepting because we try to be polite, but I think the only things that a lot of people will openly mock are lisps and stutters. And lisps even more I think because it's been used for comedic effect for a long time. I used to get mocked a lot for my stutter when I was younger, but these day I mostly get these weird looks that seem to say "poor guy", which in a way makes it even worse. Like no one really takes me seriously because I can't talk right.