Trivia: When Dan and Hollis hear a TV news report referencing Rorschach, they glance at the screen in time to see grainy black and white 'file footage' of Rorschach walking quickly away and to the right of the camera position, glancing back over his right shoulder momentarily. That footage is intentionally designed to precisely mimic the infamously-disputed film of Bigfoot (known as the Patterson-Gimlin film of 1967). (00:17:50)
Trivia: This is for the trailer rather than for the final film, but worth a look. At 1:33 in the trailer, just after seeing Rorschach slam someone against a wall, we see another fight. Pause it and look at the guy in black - he's holding a walkie-talkie, which in the next shot becomes a gun. This is only trivia, not a mistake, because it's only valid for the trailer. The MPAA don't allow guns to be pointed at the screen in trailers, so Zack Snyder, in a tribute to the infamous gun-editing from E.T., replaced the gun in that one shot with a walkie-talkie. (00:01:30)
Trivia: The plot to force peace by uniting against a common enemy is similar to the Outer Limits episode, "The Architects of Fear." A nod to this is that just after the scenes in Antarctica, you see a TV with the classic Outer Limits opening.
Trivia: On the countdown screens at the end of the movie, written below the timers it says "S.Q.U.I.D." A little nod to how the explosion went down in the graphic novel.
Trivia: In the Watchmen timeline, Rorschach's polymorphic head mask was supposed to be a commercialized offshoot of Dr. Manhattan technology. It was a double-layered, temperature-sensitive fabric that changed patterns in response to fluctuating body heat, and it was originally intended to be marketed in the garment industry. That is where Walter Kovac (Rorschach) discovered the fabric, when he worked for a dressmaker in his youth. He privately used samples of the fabric to create his own head mask. Unfortunately, the novelty fabric was a commercial failure in the Watchmen timeline, which is why we don't see it used anywhere else in the Watchmen film.
Trivia: Halfway through the film the camera pans a street and passes over a news stand run by an old man with a boy sitting against a fire hydrant reading a comic ("Tales of the Black Freighter", which has been animated and will be released on DVD). There is no time to expand the characters for the film but in the comic they play a larger role and provide the location where Rorschach catches up with the news.