The fake Agent names Sam and Dean use, Greer and Ehart, are two members of the band Kansas. Kansas is the band the performs the song "Carry On Wayward Son" which often appears in the season finale episodes and fans think of it as the theme song.
While talking to Metatron, Chuck say he was busy writing another book-series: Revolution. Revolution was a TV-Show written by Eric Kripke, who was also the creator/writer of Supernatural.
The deputy who calls in the fog on her radio uses the call sign 3-William-56, which is Riggs and Murtaugh's call sign in Lethal Weapon (1987).
When Chuck finishes the book he punches himself in the arm. A nod to The Breakfast Club when Brian Johnson (Anthony Michael Hall) does the same thing after finishing everyone's essay.
The title of this episode is a play on a running joke from the 1982 comedy film Airplane, where one character, when told something hard to accept, says "Surely you can't be serious?" to which the other responds "I am serious, and don't call me Shirley."