Possibly the most obscure Simpsons joke ever

I was just watching "Today I Am a Clown", the sixth episode of The Simpsons' fifteenth season and think I have spotted the most obscure Simpsons joke ever. Maybe I am the only person to have ever have spotted it, but then again probably not.

Anyway the joke set-up is when Krusty walks down the Jewish Walk of Fame to find he is not there but Chaim Potok is ("who's he a Klingon?"). The pay-off is the board outside the Jewish registration centre which says "Where the chosen get chosen".

Why so funny/clever, well Chaim Potok's best known novel is "The Chosen", obscure but it made me chuckle in a sort of "I get the in-joke" way.