As "The Simpsons" popularity died down, "Family Guy" emerged. A real rivalry developed between the two shows that went beyond vying for ratings and viewership.
It was technically the "Simpsons" writers who threw the first stone. The 2002 episode "Treehouse of Horror XXIII" showed us a crowd of Homer clones, including one Peter Griffin.
In the 2005 episode "The Italian Bob," the Italian police leafed through a book of American crimes. One page read "Plagiarismo," again showing Peter Griffin.
"Family Guy" threw in their own jabs at "The Simpsons" over the years, but none drew quite as much attention as one joke in the September 2007 episode "Movin' Out (Brian's Song)."
The episode shows a serious discussion between Brian and Lois, a bumper for "The Simpsons" appears at the bottom of the screen, featuring a miniature Marge waving to the audience.
At the time, many viewers mistook it for a genuine promotional ad for "The Simpsons," but things quickly took a turn. Quagmire attacked Marge and then shot her and her family.
The gag didn't land well and was decried by fans and critics as a gross and spiteful sequence and a disproportionate response to the jokes "The Simpsons" made at their expense.
The network forced "Family Guy" to cut the joke, claiming it felt weirdly personal and inflammatory, although they allowed it to be shown on DVDs and Adult Swim reruns.