This article is from the The Simpsons FAQ, by Ondre Lombard firstname.lastname@example.org and Andrew Gill email@example.com with numerous contributions by others.
There was a protest over the 1987 airing of a scene in which Maggie sticks
a fork in an electric socket. The scene was clipped from the Fox reairing,
and wasn't shown in syndication, either.
The scene, however, was based upon an actual incident, according to David
Silverman. As a boy, MG was at a party when the lights flickered. A
moment later, a boy walked into the room holding a fork. He pointed to it,
and said, "Hot."