The War of Art (The Simpsons) Lisa's new pet guinea pig destroys the Simpsons' living room art, Marge falls in love with a beautiful painting at the Van Houtens' yard sale, which Homer purchases for $20. Marge removes the frame and finds that the painting bears the signature of Johan Oldenveldt, an artist of some renown. An art appraiser estimates that it could bring between $80,000 and $100,000 at auction. Marge wants to share the sale proceeds with the Van Houtens, but Homer disagrees, saying that the Simpsons should look after their own financial security first and keep the sale a secret from them. Milhouse eavesdrops
The Simpsons Guy Appel then asked for permission from "Simpsons" executive producers Matt Groening, James L. Brooks and Al Jean to use their characters. This was approved; Appel was previously a writer-producer on "The Simpsons" for four seasons, and retained his former colleagues' trust. Dan Castellaneta, Julie Kavner, Nancy Cartwright, Yeardley Smith and Hank Azaria guest star as their "Simpsons" characters, but Harry Shearer, the final main cast member of "The Simpsons", was unavailable. Asked how he felt about the crossover, Shearer replied, "Matter and anti-matter." "Family Guy" writers pitched several storylines for the crossover, including one in which the Griffins stay with