During the hotel room scene, Alex Withrow told Chris Warner to hit on his real life sister, Catherine. Catherine, unbeknownst to any of this, was stunned when her brother spoke. Her surprised reaction can be seen in the final film.
Alex Withrow didn't shave throughout the entire shoot, a superstition he modeled after Darren Aronofsky.
Throughout filming, the cast and crew repeatedly tried to trick Alex Withrow into explaining the ending of the film.
During shooting, stars Andrew Tolbert and Claire Wagner had been dating in real life for over a year.