We don't know much of anything about the upcoming 'Superman' film for certain, except that Zack Snyder is directing it and Henry Cavill will don the iconic red and blue tights. That hasn't stopped the rumor mill from churning out numerous casting stories in the past week, including two intriguing, but most likely improbable, gossip bits about who might appear alongside the Man of Steel.

First up is news from THR's Heat Vision blog. Their sources are saying that Snyder and producer Christopher Nolan have marked 'Lord of the Rings' star Viggo Mortensen as a person of interest to play the villainous General Zod.

Zod, who originally appeared in the comics, is best known as the lead baddie in 'Superman II,' where he was portrayed by Terence Stamp. Mortensen would make for an interesting choice, for sure, although we can't shake the feeling it feels a bit safe.

Mortensen isn't a lock for the part at this point, plus he's still in the running for Universal's 'Snow White and the Huntsman.' If he lands that part, it seems unlikely that he'd be able to shoot both it and 'Superman' -- at least not without major scheduling shifts.

Hit the jump for more casting rumors.