Tonight's the night. Who's it going to be?
Promo photo went out showing the Simpsons standing over a grave with Sideshow Mel. All the men are wearing yarmulke. We know it's a Krusty episode, and it's titled Clown in the Dumps, which suggests he's upset about something.
I'm going to go with the prevailing internet theory that it's Rabbi Krustofski, and not Krusty himself.
1. Jackie Mason won an Emmy for the role
2. Krusty's death has already been done
3. Simpsons writers don't seem brave enough to kill off an important secondary character
David Hyde Pierce is a confirmed guess star, which makes Sideshow Bob a possibility, but that may be a red herring. Bob also isn't Jewish. That's assuming the promo photo isn't a red herring itself, as Krusty is missing.