Well, more accurately, Temple of Doom was why the PG13 rating was made. People freaked at how dark and violent it was, and Spielberg suggested the new rating for future films. I believe Dreamscape was the first mainstream feature film with the rating.
There was a 2003 study that demonstrated that puppets getting randomly tossed in the background is funny 89% of the time, but foreground tossings are only funny 17% of the time. Further research is needed to discover the cause of this discrepancy.