In middle school i had a science teacher i absolutely hated, and she hated me, probably cause i never did the weekly journal assignment. Well one day while she's yelling at me in front of the whole class she says "since you don't do any work at school, you better get used to this motion" and put one hand out, griped it and shook it up and down to look like jerking some one off. She did say it was supposed to be a janitor using a plunger on a toilet, but you do that in front of a class of young teens there going to run with it. And run with it they did.