Ever since ditching meat for good in the season seven episode, Lisa the vegetarian, Lisa Simpson has become one of the most famous vegetarians in the world (even if she is a cartoon character). 

However, the Simpsons writers never intended for that to be the case. According to Hank Azaria, they only made the decision to make her a vegetarian because it was the only way Paul McCartney would agree to cameo on the show.

Azaria told the Huffington Post that the former Beatle's main stipulation for guest starring was that they made Lisa become a vegetarian and never eat meat again for the rest of the show. 

“I thought it was really cool that he stuck that [in],” Azaria said. "I can tell you, over the years, they were tempted a bunch of times to have Lisa break her vegetarian vow.”

However Azaria thinks that the writers will stick to their word. 

“No, you don’t break a knight’s vow. As we’ve learned from ‘Game of Thrones,’ you do that at your own risk.”

So there you go. Turns out you do win friends with salad.