"Batman vs. Superman" director Zack Snyder continues to tease fans about the upcoming production, revealing his reactions to test shots of all three superhero costumes.

In an interview with Forbes, the "Man of Steel 2" director explained what he found to be the most "fascinating" part of working on the film, which is slated to hit theaters on May 6, 2016.

"The thing also that's really fascinating for me is that, even just in the tests we've been doing, the costumes, right? You basically have Batman and Superman - and this is without Ben [Affleck] and Henry [Cavill] in the costumes, but just like the stand-ins, just testing to see what the costumes look like," Snyder told Forbes.  "And  you have them standing there and they're standing in the same shot - and then we have Wonder Woman, you know, all three of them in the same shot. Even just for a test, you really have to go, 'Wow, that's crazy!'"

"Not only is it the first time that I'm seeing them, it's the first time they've ever existed together on screen in a movie," he continued.  "And that's kind of a huge deal. Even just Batman and Superman standing next to each other... [I]t's kind of epic. You do sort of sense the weight of the pop culture iconography jumping out of its skin when you're standing there looking at the two of them and Wonder Woman. It's crazy. But it's fun. I mean, I have the first photo, I've got it in my archive because I was like, 'Okay, I better keep this, it's gonna be worth something."

Snyder explained the development process for "Batman vs. Superman," which began soon after the original "Man of Steel" reboot wrapped.

"I gotta be honest, it definitely was a thing that... after Man of Steel finished and we started talking about what would be in the next movie, I started subtly mentioning that it would be cool if he faced Batman. In the first meeting, it was like, "Maybe Batman?" Maybe at the end of the second movie, some Kryptonite gets delivered to Bruce Wayne's house or something.  Like in a cryptic way, that's the first time we see him. But then, once you say it out loud, right?" the director told Forbes.

"You're in a story meeting talking about, like, who should [Superman] fight if he fought this giant alien threat Zod who was basically his equal physically, from his planet, fighting on our turf," he continued.  "You know, who to fight next? The problem is, once you say it out loud, then it's kind of hard to go back, right? Once you say, 'What about Batman?' then you realize, 'Okay, that's a cool idea. What else?' I mean, what do you say after that? ...But I'm not gonna say at all that when I took the job to do Man of Steel that I did it in a subversive way to get to Batman. I really believe that only after contemplating who could face [Superman] did Batman come into the picture."

You can read Snyder's full interview with Forbes here.