Sometimes I remember something from long ago, like Matt Groening saying something like "Frank Zappa is my Elvis." And then plug that into The Googles to see what turns up. Frank did some cartoon voice work (The Powdered Toast Man was classic), but The Simpson gig never panned out.
Sometimes I take a band or musician I really like and go from there. I couldn't find any recording that Tony Levin did with Zappa, but he is a couple of Debris of Zapparation away. In 1970, Levin moved to New York City, joined a band called Aha, the Attack of the Green Slime Beast, with Don Preston of The Mothers of Invention. Lately he's been playing with Terry Bozzio, among others.
And then there the great band Los Lobos and their 1993 20th anniversary album, Just Another Band From East L.A., obviously a nod to the Mothers LP "Just Another Band From L.A". I couldn't find any reference to Los Lobos working with Frank, but googling "Los Lobos Frank Zappa" turned up this:
Rubén Funkahuátl Guevara is a singer, songwriter, producer, writer, poet, performance artist, and impresario. He made his mark in music with his 1970s band Ruben & the Jets, who recorded two albums on the Mercury Record label, the first produced by the legendary Frank Zappa
In 1958, Rubén and Pablo Amarillas formed the Apollo Brothers, who were influenced by Don & Dewey and the Carlos Brothers. They performed at the El Monte Legion Stadium, Alan Freed's Record Hop at Jordan High in Watts, Pacific Ocean Park, and various local television shows. They recorded for Cleveland Records and were the first Chicano duo to be played as a VIP platter on KGFJ, a Los Angeles rhythm and blues station
In 1965, Rubén performed solo on the hit national television show, Shindig. He was on the bill with Bo Diddley, Tina Turner, and Jackie DeShannon. Rubén opened the show in a medley with cast, sang a solo spot, and closed the show with Bo Diddley. Rubén's rendition of Bobby Blue Bland's "Don't Cry No More" went over so well, the producers wanted him to replace singer P.J. Proby, who had left the show.
In the late 60s, Rubén went to Los Angeles City College and studied music composition and modern composers for two years. This education was of help when he worked with Lalo Schiffrin on the soundtrack for Clint Eastwood's "Coogan's Bluff," in 1968, and his later work with Frank Zappa.
In 1969, Rubén went to a Frank Zappa and the Mothers of Invention concert at the Shrine Auditorium. Zappa had just put out a parody doo wop record called "Cruisin' with Ruben & the Jets." Rubén got backstage and thanked Zappa for bringing back that kind of music and told him that his name happened to be Rubén and that he sang in that style. Two years later, Rubén went to Zappa's house with a friend, keyboardist Bob Harris, who had toured with Frank. After spending hours listening to records and talking about music, Zappa and Rubén found that they liked much of the same music, rhythm & blues and doo wop, as well as modern composers such as, Varese, Bartok, Stravinsky, and Cage.
Zappa asked Rubén if he'd be interested in forming a real Ruben & the Jets. Rubén put the band together and auditioned for Zappa, who wound up producing their debut album on Mercury Records called "For Real." The album is classic doo wop and rhythm & blues. They did covers of Chuck Berry's "Almost Grown," Joe Houston's "All Nite Long," a soulful version of "Dedicated To the One I Love," which features a great guitar solo by Frank Zappa, and "Charlena," which was later also covered by Los Lobos.
Go read the whole thing, as they say.