'The Simpsons' Returning Homer's Greatest Enemy for 600th Episode

Season 28 is shaping up to be a big one for The Simpsons; not solely for the series’ first hour-long special, or even the 600th episode, but also some of the familiar faces popping up. To wit, the joint Treehouse of Horror and 600th episode will feature the return of one of Homer’s greatest adversaries, as the famous Frank Grimes pops in from beyond the grave.