We all know what a classic video game trailer looks like. The close-up of the monster. A scene or two of awesome gameplay. Some witty dialogue. The shot of the hero, looking pensive, with his hair blowing in the wind or backlit by an explosion. Or both.

Ads for "The Bureau: XCOM Declassified" take on the feel of a pulp-horror film. (Courtesy 2K Games)

The trailers for "The Bureau: XCOM Declassified," buck all those conventions -- including the one that says you have to show part of the actual game. And that's exactly what's made them so successful.

Instead of a boilerplate trailer, 2K Games asked director Henry Hobson to make six live-action trailers starring "Lord of the Rings" star Dominic Monaghan, plenty of aliens and a disturbed clown that Hobson said he found after the creepiest casting call in entertainment history. Pieced together, they become a short history on how the alien-fighting XCOM division got its start, as well as an excellent illustration of how the gaming world is thinking outside the console when it comes to crafting its advertising campaigns.

The idea of creating an expanded universe is nothing new to the gaming world -- there are novels, comic books and Web series galore out there to prove it. But studios are thinking more than ever about how to build buzz and communities around their biggest titles, and how to pull non-gamers into the mix as well. Efforts like XCOM trailers or the Steven Spielberg's expected "Halo" television series are made to expand a game's appeal.

For the short trailers, director Harry Hobson said he consciously tried to approach the project without using his gamer's eye and instead aimed to make them as cinematic as possible. The result was a run of trailers that felt more like a Web series -- several commentators on the videos said that they would like to see a full movie done in Hobson's pulp-horror style.

Yet while the commercials can stand alone, Hobson, who has directed game trailers in the past, was sure to incorporate plenty of throwbacks to the XCOM franchise throughout his series. That came not only out of deference to the game designers, who've spent years developing the title, but also to the series' longtime fans.

To strike that balance, Hobson dropped plenty of Easter eggs into the spots, as well as weaving elements in that made watching the trailers more like a game itself. One of the trailers asked the audience to choose the ending, via Twitter vote. A telephone number shown for just a couple of frames turned out to be an actual, working number that played audio from the trailers. And Hobson deliberately put aliens in the background of shots, just to see if fans of the series would pick up on the small touches.

Taking this approach to build up a game can also help studios distinguish their titles from the pack. "The Bureau: XCOM Declassfied" is a big release, but the third-person tactical game isn't exactly a marquee title. It could have easily been lost in a summer haze.

While we won't know how successful the trailers have been until the game is actually released, the trailers have at least done their job of getting people talking. Commentators combed through the scenes, sharing their theories about the trailers' plot and what it may say about the game. Some even put up frame-by-frame analyses of each trailer as it came out, setting up even more places for conversation to flow.

"If you can find the right frame, find other little mysteries to put in, those things let the pure gamers get excited -- as well as the non-traditional gamers like myself," he said. "This live-action trailer has become almost interactive, doesn't have to be a one-way street."

In fact, the chatter around the trailers made Hobson want to pack even more clues into the spots and leave some red herrings around for good measure.

Fanning the flames of speculation, however, can backfire. And, as Hobson learned, sometimes it's personal. One "clue" fans picked up was a shot of his own hand, holding a door. But in a frame-by-frame review of the spot, Hobson said, the analysts stopped the trailer, circled it -- and identified it as the hand of an alien.