Actually, I think it's going to be Krusty's father, Rabbi Hyman Krustofski. Like Al Jean hinted, he's a character who's voice actor won and emmy award. Plus, Jackie Mason, the person who voice Hyman, is getting so old with a declining voice that he just simply cannot voice the character any longer.

It would also add meaning to the title, "A Clown in the Dumps", as it could mean that Krusty is sad over the loss of his father.

This show is losing too many characters. Troy McClure, Maude Flanders, Mrs. Glick...