He appeared as Stephen's guest on the November 29, 2005 edition of The Colbert Report and then again on the May 7, 2007 edition of The Report. Preston is a scary guy who has studied scary diseases. He doesn't think the type of smallpox that make you bleed out of your ass is 'the extreme smallpox,' he thinks of it as 'ordinary smallpox.' The bad kind makes your skin slip off your body in sheets and turns the whites of your eyes black. He has also written an entire book devoted to enviroporn.