The very first Simpsons Treehouse of Horror episode premiered in October 1990. Fox executives were so concerned about placing a horror themed episode on a cartoon show that they ordered a warning to be placed before the show. Not wanting to alarm their audience with the standard "parental guidance is advised" warning, the writers devised a tongue in cheek warning to be presented by Marge Simpson.
After the fifth Treehouse of Horror episode aired, the network seemed to forget about the warnings and the writers on the show were more than happy to drop the segment from that point on.
