There are great mysteries of our age: who built the Pyramids? Are there aliens in Area 52? And what's up with Scoot McNairy's legs?

Specifically, what's up with the green screen tights on his legs in these spy pics Batman-News snagged from the set of "Batman V Superman: Dawn Of Justice?"

Given the intense secrecy around the movie, which includes just what frequent Ben Affleck collaborator Scoot McNairy is playing in the film, there's not a lot to go on from a picture of some tights. Still, we've got a few possibilities:

The Flash

This is the most frequent guess from fans online, that McNairy's legs need to be green screened because he'll be running fast as DC's Scarlet Speedster. Still, there's no confirmation that the character – soon to be seen on TV in his own CW series – will appear in "Batman V Superman," let alone that the production would need to digitize just his legs for speed.

Unless he's running like this:

Metallo

The Superman villain is powered by Kryptonite, and more man than machine. Could Scoot have robot legs, and more robot parts beyond that? Sure, why not! We know the heroic Cyborg appears in the movie, or at least his human alter ego Victor Stone, so maybe McNairy is also sporting some sweet metal feet.

His Legs Get Cut Off

With literally no knowledge about the plot of the movie this is the most likely possibility. McNairy is still wearing business attire, so unless he's just chilling in his "Halt and Catch Fire" costume to cover up a full green man suit, it looks like he's going to lose his legs at some point. Poor Scoot.

Legs

Speaking of legs, maybe Scoot is playing Legs, a homeless Vietnam Vet who appeared throughout Batman comics in the '90s. Legs lost his legs, hence being called Legs. In the comics, Legs worked for a villain named Anarky, though no word on whether the baddie appears in "Batman V Superman." Also, McNairy doesn't look very homeless, not to throw out any stereotypes, but you know, business suit. So he's probably not playing Legs. Related: legs.

He's Rocking The Latest Fashion Trend

What if "Batman V Superman" takes place in an alternate reality where the hottest fashion trend is to wear green screen socks and sandals? What if? Wouldn't that be great? So great.

Why do you think Scoot McNairy's feet are green screened? Let us know in the comments below.