This is just hilarious. Steve Martin was on "The Colbert Report" to promote his new novel, "An Object of Beauty" which is set in the New York art world. Martin is also an avid art collector.
Instead of a discussion about the book, Colbert asked Martin to assess the value of a portrait of Colbert. The bit evolved to include famed artists Frank Stella, Shepard Fairey, and Andres Serrano, all of whom contributed to the portrait's "value." The Serrano conversation is priceless. You will laugh, I promise, and Martin is so charming.