Batman v Superman: Dawn of Justice
Batman V Superman: Dawn of Justice is the sequel to Zack Snyder's Man of Steel. Warner Bros

So far, the Batman v Superman team has done a good job of keeping key details about the film a secret. But that doesn't stop fans from speculating.

After several reports regarding Aquaman's presence in the film, the focus has shifted to rumours about another big-name DC superhero appearing in the upcoming movie.

Actor Scoot McNairy's role in Batman v Superman: Dawn of Justice is still a mystery, but a new on-set photo of the actor, taken on 18 August 18, reveals a major clue, according to Batman-news.com.

Scoot McNairy's legs being green screened on the set of #BatmanVSuperman. Infinite number of possibilities.. pic.twitter.com/1McfKo9WFg

— Sean Atkins (@SeanJ8) August 19, 2014

Here's what those green socks mean: the special effects team are going to digitally do something to those legs during post-production. Now what could that really mean?

The Flash
The Flash is one of DC Comic's most popular second-tier superheroes, behind Superman, Batman and Wonder Woman. DC Comics

One, among several possibilities, is that McNairy might actually be playing: The Flash.

We know that the BvS team is filming some major action sequences set amid a lot of destruction and chaos. Maybe those scenes will feature The Flash in action trying to save lives – it might be a key scene that reveals the speeding superhero to the audience. Just a theory.

However, seeing that The Flash is one of the primary superhero characters and member of the Justice League, maybe it's not unwarranted to assume that director Zack Snyder definitely has a part for him somewhere in the film.