 At the time the episode was being written , Paul McCartney was the only living member of The Beatles who had never appeared on The Simpsons . John Lennon died before the show was created , but Ringo Starr and George Harrison had guest starred in 1991 ( " Brush with Greatness " ) and 1993 ( " Homer 's Barbershop Quartet " ) , respectively . The Simpsons staff wanted to bring McCartney onto the show , and David Mirkin thought " Lisa the Vegetarian " would be an attractive story , since McCartney is a vegetarian himself . McCartney agreed to appear , but requested that Lisa remain a vegetarian for the rest of the series , rather than revert to meat @-@ eating in the next episode . The Simpsons staff promised that she would remain a vegetarian , resulting in one of the few permanent character changes made in the show . McCartney 's wife Linda was also recruited to appear in the episode . She told Entertainment Weekly that the episode was a chance for her and her husband " to spread the vegetarian word to a wider audience . " Paul and Linda were both long @-@ time fans of The Simpsons . 
