Parents Music Resource Council.

Basicly, they're a collection of rich senator's wives (Tipper Gore co-founding it) and are largely responsible for the "Parental Advisory" labels we see today. They were looking for more though. Frank Zappa, John Denver, and Dee Snyder (Twisted Sister) were the only three artists to testify against them in congress. Zappa wrote his album "Frank Zappa Meets the Mothers of Prevention" about this experience.