In the 2004 book "Planet Simpson", Chris Turner quotes Bart's revelation to Lisa that he sold his soul to Milhouse for five dollars and used the money to buy sponges shaped like dinosaurs. After Lisa criticizes Bart for selling his soul, Bart responds: "Poor gullible Lisa. I'll keep my crappy sponges, thanks." Turner comments: "Here Bart is the epitome of the world-weary hipster, using the degraded language of modern marketing to sell off the most sacred parts of himself because he knows that some cheap sponge is more real, hence more valuable, than even the loftiest of abstract principles."