Paul McCartney only agreed to appear in The Simpsons if there was one major change to main character

Music legend Paul McCartney wasn’t willing to appear on the Simpsons unless the creators agreed to a major change he had about one of the key characters.

The Simpsons has been running... well, as long as we have been recording history, I think.

Spanning 35 seasons, a feature length film, and multiple specials, the show has seen a whole host of celebrity guest appearances, either as themselves or random new characters.

One memorable one is Beatles member and music legend Paul McCartney way back in 1995, during the seventh season.

Paul McCartney had some demands for the showrunners when it came to his Simpsons appearance(Joe Maher/Getty Images)

But McCartney, who guest-starred with his late wife Linda McCartney, had some conditions he wanted met before he got on board, and it concerned Lisa Simpson.

Obviously, with Lisa being one of the key members of the Simpsons family, you can imagine there might be some pushback, but the creators seem to have kept their word.

McCartney featured in the episode “Lisa the Vegetarian”, where the 8-year-old decides to stop eating meat after meeting the cutest little lamb at a petting zoo.

McCartney agreed on the promise that the creators would keep Lisa a vegetarian for the rest of the series.

Speaking to G2 magazine, McCartney explained his thinking behind it.

He said: “We were a bit worried that she would be a vegetarian for a week, then Homer would persuade her to eat a hot dog.”

McCartney has said the showrunners have kept their word on keeping Lisa vegetarian(Disney)

This news eventually spread around social media, and on Reddit, Simpson fans were respected the move.

“So THATS why her being a vegetarian stayed a part of her character. I couldn't imagine her any other way now but once upon a time lol,” one person wrote.

“It does sit well with her character, and the writers probably took it as a suggestion,” another commented.

“I became a vegan when I learned about this. I obviously didn’t realize what any of it meant as a kid. As an adult, it’s inspiring," a third wrote.

"For me, it's a perfect example of notoriety put to good use!" another wrote.