basis of Homer and Lisa's dispute. George Meyer, a writer known among the staff for his "bizarre physical jokes", contributed the idea of the barbecue pig getting caught in the spillway and flying into the air. Cohen credits writer John Swartzwelder for inspiring the scene in which Homer finds it impossible to believe that bacon, ham, and pork chops could possibly come from the same animal. According to Cohen it was based on a real statement made by Swartzwelder, who was going on and on about how amazing the pig is for the variety of cuts of meat that come from it. Voice acting 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 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 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. Mirkin later said that recording with the McCartneys was one of the most "amazing" experiences of his life. He flew to London and met the couple at Paul McCartney's recording studio, where the McCartneys spent an hour recording their parts. The Simpsons creator Matt Groening was supposed to go with Mirkin to London, but missed his plane. Groening commented that having McCartney and the rest of the Beatles on The Simpsons "was a dream come true for all of us". Linda McCartney died of cancer at age 56 on April 17, 1998. The Simpsons' season nine episode "Trash of the Titans", which aired on April 26, 1998, was dedicated to her memory. Executive producer Mike Scully said, "It just seemed like the right