If you need to be reminded that Jon Favreau is a super nice guy, beloved by all, and a director who runs a great set, all you have to do is look at Cowboys & Aliens. It was supposed to be a dusty reunion for Favreau and Robert Downey Jr., but another Iron Man 2 star has eagerly signed on instead. According to THR's Heat Vision, Sam Rockwell has joined the cast of the sci-fi western, alongside Harrison Ford, Daniel Craig, and Olivia Wilde.

Rockwell will be playing Doc, a saloon owner who gives up hawking rye whiskey in order to fight aliens. According to Heat Vision, the part of Doc was originally a small one, and was designed for a beefy, heavyset guy. But once Rockwell showed interest in the film and the role, Favreau and writers Alex Kurtzman and Roberto Orci completely rewrote the part. Now Doc will be a major player in the battle. I guess he will also be a slighter fellow, who favors smarts over cracking heads or something. (That's no slam on Rockwell, by the way. Don't read it as some kind of slam on his physical attributes which I think are just fine for any role!)

Cowboys & Aliens begins shooting (both on film and onscreen!) in June, and is aiming to hit theaters on July 29, 2011. Despite its silly premise -- Apaches and cowboys team up to fight off an alien invasion -- I really think this might be one of the big surprises of Summer 2011. It might be worth a ticket just to see this cast in their cowboy costumes, right?