When the McCartneys made a cameo on “The Simpsons,” it was a marriage between two of the most popular cultural entities in contemporary history.

To get Sir Paul McCartney on the show, the team behind the animated series had to make the musician a premise-altering promise ― that the young Lisa Simpson character would become a vegetarian like the McCartneys and never be considered a meat eater ever again.

The cameo occurred in the aptly titled episode “Lisa the Vegetarian,” which aired in the fall of 1995 during Season 7. Paul appeared on the show with his then-wife, Linda, and taught Lisa about the values of a plant-based diet. He even revealed to Lisa that “if you play ‘Maybe I’m Amazed’ backwards, you’ll hear a recipe for a really ripping lentil soup.”

In a recent interview with Hank Azaria about his Emmy nomination for “Ray Donovan,” The Huffington Post had the chance to ask the longtime “Simpsons” voice actor and other star of “Lisa the Vegetarian” about what it was like to have McCartney on the show.

Apparently, the writers have debated breaking their famous deal with McCartney.