Furthermore, how come there's never been any concrete Zappa reference on The Simpsons?
I'm convinced that in one variation of the opening sequence, Lisa plays a few bars of King Kong as she walks out of the classroom. I've seen it a couple of times now, but haven't managed to get a tape of it yet for group verification.
i'll second that observation; i've seen it too. it is most certainly "king kong". i wish i could remember what episode it was in.
Lisa plays some notes of King Kong (very fast) in these episodes:
AABF14 Simpsons Bible Stories—season 10
CABF01 Lisa the Tree Hugger—season 12
CABF02 The Computer Wore Menace Shoes—season 12
CABF06 Skinner's Sense of Snow—season 12
There is actually a Mothers of Invention reference in the very last season of the simpsons ("The Girl Who Slept Too Little", Season 17, episode 02). At approximately 7 minutes and a half, you could see a sign in the entrance of the stamp museum that says "Fathers of Invention" in big letters. Over it, there is a graffiti saying "and Mothers". Therefore it says "Fathers (and Mothers) of Invention" ...
Last weeks Simpsons with Cheech & Chong
At about 2:46 the Crawdaddy Magazine on the floor features FZ on the cover
Maintained by Román García Albertos
The Simpsons #480, Season 22, Episode 16, NABF09, "A Midsummer's Nice Dream," March 13, 2011—3:28