Yankovic came up with the idea for "Fat" while watching the "Bad" music video, when he had an epiphany that a parody of that song titled Fat would be a good sequel to "Eat It" (a previous Weird Al Michael Jackson parody). As he watched the "Bad" video, he imagined an obese version of himself trying to get through the turnstiles on a subway, and resolved that he would do it.
When performing in concert, Yankovic wears a fat suit and a mask that makes his face appear fat. Due to undergoing laser vision correction surgery, he no longer needs to wear glasses, though he wears glasses with non-prescription plastic lenses in order to help hold on the mask.
The video won a Grammy Award for Best Concept Music Video in 1988.
It is Yankovic's second parody of a Jackson song, the first being "Eat It", a parody of Jackson's "Beat It".