Paul McCartney Had One Condition For His Cameo In The Simpsons

So many celebrities have appeared on "The Simpsons," that 36 seasons later, the cameos have become a crutch for the show. Worse, the guests have gone from voicing characters (take Dustin Hoffman's uncredited appearance in "Lisa's Substitute") to just appearing as themselves. 

The cracks were already showing in the show's golden age. Season 7's "Lisa The Vegetarian" features Paul and Linda McCartney showing up at the end to reassure Lisa she's made the correct choice of vegetarianism. The McCartneys are depicted as friends of fellow vegetarian Apu Nahasapeemapetilon (Hank Azaria), who tend to his secret garden on the roof of the Kwik-E-Mart. After Lisa and the meat-loving Homer reconcile at the end, McCartney's "Maybe I'm Amazed" closes the episode out.

Paul McCartney was the last surviving Beatle to cameo on "The Simpsons" (Ringo Starr beat him to the punch in season 2's "Brush with Greatness", followed by the late George Harrison in season 5's "Homer's Barbershop Quartet"), and he's far from the most loathsome Englishman to appear on the show (that'd be former Prime Minister Tony Blair). But this cameo came with a demand that had series-long ramifications: Mr. and Mrs. McCartney wanted Lisa to remain a vegetarian. Not just at the end of the episode, no, but for the entirety of the series henceforth. 

"The Simpsons" generally abides by the writing rule that TV Tropes calls "Aesop Amnesia," where character development never sticks past one episode. It's easier to write sitcoms when your characters have to constantly learn lessons. Since the McCartneys were genuinely passionate vegetarians, though, they wanted Lisa to join their community and never leave. 

McCartney recounted in a 2020 interview with GQ: "We were a bit worried that [Lisa] would be a vegetarian for a week, then Homer would persuade her to eat a hot dog. The producers of the program assured us that she would remain that way and they kept their word."

Speaking to the Radio Times, former "Simpsons" showrunner David Mirkin said, "Every time I see [McCartney], he always checks and he's always surrounded by nine or 10 lawyers, so it's quite frightening!"

"Lisa the Vegetarian" was written by soon-to-be "Futurama" co-creator David X. Cohen. It was his first full-length "Simpsons" script; he previously wrote the short "Nightmare Cafeteria" for "Treehouse of Horror V," in which the Springfield Elementary faculty begin cooking and cannibalizing the student body. That short will make meat look even less appetizing to you than "Lisa the Vegetarian" will!

Mirkin himself is a vegetarian, so he was happy to approve Cohen's pitch and to grant the McCartneys' condition for their cameo. As the "Talking Simpsons" podcast has noted, though, Lisa remaining a vegetarian "forever" probably meant something different to Mirkin then than it does now. At the time, the "Simpsons" staff didn't know the show would go in apparent perpetuity. When "Lisa the Vegetarian" aired in season 7, they were probably expecting the show would wrap up soon. So when Mirkin made his promise to McCartney, he could've thought it would be a rule they'd only have to uphold for two or three seasons, not an edict he'd be passing onto 30 seasons' worth of future writers.

Azaria didn't actually meet the McCartneys despite technically sharing a scene with them, but he praised McCartney's role in making Lisa a vegetarian (via the Huffington Post):

"I thought it was really cool that he stuck that [in]. I can tell you, over the years, they were tempted a bunch of times to have Lisa break her vegetarian vow. [The writers] probably have not because they made that vow to Sir Paul."

The closest the show has come to breaking the promise, as long-time "Simpsons" showrunner Al Jean told /Film in 2018, is showing Lisa eating meat during flashback scenes. In the 2023 episode "Ae Bonny Romance," Lisa eats a Scotch egg when the Simpsons visit Edinburgh; realizing too late that it contains meat, she spits it out in shame.

After all, it's not just McCartney keeping an eye on the writers now — their vegetarian fans are too. Some vegetarians/vegans credit Lisa Simpson for helping their own journey, and in 2016, there was a widely-signed petition to make her "level up" into a vegan. Just further proof that Paul McCartney's impact on the world didn't end after the Beatles' break-up.