The War of Art is the fifteenth episode of Season 25, that premiered on March 23rd, 2014.
Synopsis
After Lisa's new pet guinea pig destroys the Simpsons' living room art, Marge falls in love with a beautiful painting at the Van Houten's yard sale, which Homer purchases for $20. Marge dislikes the frame and removes it, revealing a previously invisible signature "Johan Oldenveldt". Lisa researches Oldenveldt and discovers he is of some fame, so Homer and Marge have the painting appraised in a loal auction house. The appraiser judges the painting to be valuable, and estimates it could auction for $80,000-$100,000.
Marge thinks the proceeds from the painting's sale should be shared with their friends, the Van Houtens, but Homer thinks for the Simpsons' future financial security they should keep the money for themselves. He eventually persuades Marge that the Van Houtens would dislike knowing they had missed the painting's value and sold it cheaply, but Milhouse, who is in Bart's treehouse, overhears the conversation and eventually tells his parents.