The parody is mysterious and important.

In the Season 4 Simpsons episode, "The Front," Bart and Lisa read a letter that is implied to have a swear word.

In The Simpsons episode "Cape Feare," an Itchy and Scratchy interlude turns deadly with a suicide joke that crossed the line.

The Simpsons launched some of the animated series’ decades long traditions with its second ever episode. The Simpsons has had ...