The War of Art (The Simpsons) on the conversation from Bart's treehouse and tells his parents. The Van Houtens publicly shame the Simpsons for their secrecy, prompting a town-wide division of opinion. As the auction begins, Dawn, a former lover of Kirk's, arrives and claims that he took the painting from her. The auction is suspended until its ownership can be established. Kirk tells Homer that he bought the painting on the island of Isla Verde, home to an artists' community. Homer and Lisa travel to the café at which Kirk made the purchase in order to corroborate Kirk's account and the legality of Homer's purchase.
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