Audiences are gearing up for the first big blockbuster of the summer, 'Thor,' which hits theaters on Friday, but the brawny, little-known actor who landed the part and is about to become synonymous with the Marvel Comic superhero wasn't even on the director's original shortlist of casting possibilities, according to the Hollywood Reporter.

Chris Hemsworth, 27, is earning great reviews for 'Thor,' director Kenneth Branagh's big-screen adaptation of the classic comic, but his 21-year-old brother Liam Hemsworth ('The Last Song') was actually up for the part first.

After poring over possible actors for months, Branagh settled on four to screen test, Liam among them. However, none struck the director's fancy, so he decided to return to square one and reassess some of the actors he'd looked at previously, including Chris. A few interviews, some screen tests, a supportive phone call from a powerful friend and a video audition tape made by his mother later, Chris had the part.

"I was on the 17th floor of a hotel in Vancouver with my mom reading the lines to me," Chris tells The Hollywood Reporter of the video audition tape he made with his mother. "And something great must have happened. It got me back in the room."

It also probably helped to have the support of Joss Whedon, writer and producer of Chris's long-delayed thriller 'The Cabin in the Woods' (which is finally being released this fall), who made a phone call on the actor's behalf. Whedon is directing Chris as Thor in Disney's in-production Marvel superhero mega-movie 'The Avengers.'

Check out the 'Thor' trailer:

"We did two or three interview sessions before we tested him," Branagh says of Chris. "We pretty much knew as we were shooting the test that he was the guy. It seemed, across these meetings, he had grown into it. He understood it better. And, crucially, he was at ease."

Liam, it seems, isn't too worried that his big bro bested him for 'Thor.' "We're competitive, but in the best way," Chris says, and with the role of a lifetime landed, the actor is set to break out in a big way. In addition to 'Thor,' 'Cabin in the Woods' and 'The Avengers,' the actor has already completed work on the remake of 'Red Dawn' and is rumored to be considering 'Snow White and the Huntsman.'