After last week’s talk at the 92nd Street Y, Steve Martin was probably planning to avoid discussing all things art-related when he visited The Colbert Report last night. But Stephen Colbert was actually interested in tapping his expertise. In fact, he asked the actor and noted art collector to valuate a portrait of himself. When the original appraisal was a mere $19, Colbert brought out several famous art world guests to provide their take — and in some cases, revisions. Click through to watch Frank Stella, Shepard Fairey, and Andres Serrano in action.