During the 'nickname' section of the show, the woman who is a Shakespeare scholar is seated next to Ed Norton and the woman who's a tennis coach is seated next to Adam Levine of Maroon 5. Also, at the beginning of the show, you can see Kevin Kline in the audience.
According to Patton Oswalt on the Marc Maron WTF Podcast, originally this project was pitched by him to the producers as a faux-satirical documentary on George W. Bush by a Conservative think tank. He got writer's block and told them months later he couldn't write it. This special came about as a last minute change to fill in the gap for Will Ferrell in his Bush SNL character.
Commonand Serena Williams are clearly seen sitting in the audience behind the audience member nicknamed "Jacques Cousteau."