When Tim goes into the toilets and looks in the mirror there is a piece of graffiti that reads "EDGAR SUCKS COCKS," which was written by director Edgar Wright himself.
Simon Pegg always wanted to incorporate the pretend gunfight and the "understanding" between males, even strangers, that lead to it into his stand-up routine, but he was never able to figure out how to tell it right.
Movie reference: the group of boys flanking Duane, as well as his response, "clever boys," are a reference to Jurassic Park.