Recent images saw Captain America taking on an actor in a CGI Motion-Capture suit with some cool looking high-tech weaponry.
According to Movie Web, sources on-set stated the aliens the Avengers will be assembling against are none other than -- those darn and dirty Skrulls!
The Skrulls have been theorized for sometime, with the thought that Loki somehow summons them to earth.
There's also the thought that Loki is behind an early battle between the Hulk and the Avengers, with the Hulk coming in at the end to help out.
With the Skrulls -- will certainly bring even more questions and mystery.
Because the Skrulls are shape-shifters!
There has actually been rumor of S.H.I.E.L.D. agent Coulson thought to be really a Skrull, with Clark Gregg playing off it on twitter for quite a while.
Actually in the comics, there was a huge event throughout the Marvel Universe where the Skrulls infiltrated various governments - and super heroes! It was known as "Secret Invasion."
The Avengers assembles May 4th, 2012 and is directed by Joss Whedon, starring Robert Downey Jr. as Iron Man, Chris Hemsworth as Thor, Chris Evans as Captain America, Samuel L. Jackson as Nick Fury, Mark Ruffalo as the Hulk, Scarlett Johansson as the Black Widow and Jeremy Renner as Hawkeye.
Head on over to the Cosmic Book News The Avengers Movie Hub for more news, images and trailers.