Weird Al wrote "Beat It" as "Eat It" first, as a pastiche of the general style of Michael Jackson. Quincy Jones heard a rough mix, and talked Al into letting Michael do his version first, because he thought it was even better than the real thing. Al didn't want to do it at first, but Quincy convinced him that Michael Jackson boasting about being tough and gangsta would be even funnier.
When he heard the last bit, Jackson is reputed to have said "ow!".