Marvel’s comic-book film franchise kicks into high gear this year with the release of Thor on May 6th and Captain America: The First Avenger on July 22nd. All this is a lead up, however, to what fans have eagerly been waiting for: The Avengers. The Joss Whedon-directed flick, which hits theaters on May 20th, 2012,  starts filming soon and stars all the major Marvel characters of films past (and some new): Robert Downey Jr. Chris Evans, Chris Hemsworth, Mark Ruffalo, Jeremy Renner, Scarlett Johannsen, Samuel L. Jackson and recent addition Cobie Smulders.The plot of the film is tightly under wraps, but it appears that Marvel may have shot a secret teaser trailer for the film recently to attached to either Thor or Captain America this summer. Not only that, but the trailer reveals who the villain of the film may be. Hit the jump to find out. Beware, spoilers lurk below.Again, possible spoilers regarding the villain of The Avengers are revealed below. Last chance to turn back….......Okay, still with me? AICN is reporting that Marvel recently shot a teaser trailer with Loki, Thor’s brother (played by Tom Hiddleston in Kenneth Branagh's Thor). Now, you may remember that back in Steve’s video blog for his Thor set visit, he mentioned that the ending of that film hinted at setting Loki up as the villain for The Avengers. It looks like this all may turn out to be true.In addition to Loki, Latino Review is reporting that Thor’s archenemy will get a hold of the cosmic cube seen in Hugo Weaving’s hand in the Captain America trailer in order to summon the Skrulls to help him take over Earth.This Skrulls rumor has been around since December. The creatures are an extraterrestrial humanoid race and will presumably be very scary (Green! Reptilian! Pointy ears!).Personally, I think Marvel going all “alien” is pretty damn cool. Especially with Joss Whedon at the helm. Will audiences buy into such a sci-fi comic book movie? We’ll find out for sure when Thor hits theaters in May and audiences get their first taste of an other-worldly comic book flick. Until then, what do you think about The Avengers battling Loki and The Skrulls? Worthy adversaries? Would you have rather them battle Hulk?To catch up on all things The Avengers, click here.