Man of Steel director Zack Snyder is getting ready to start production on what may be the biggest film of his career, Batman Vs. Superman, which brings together these comic book icons on the big screen for the first time. During a new interview with Forbes, the filmmaker revealed when and why they first started discussing bringing these two superheroes together, and what it was like seeing the holy trinity of Batman, Superman and Wonderman together on set as the stand-ins first climbed into their costumes.

"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? 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... 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."

Ever since Ben Affleck signed on to play Batman, fans have been curious when we may see the first photo of the actor in costume, and Gal Gadot as Wonder Woman in costume. The filmmaker revealed that he has a photo of these two actors along with Henry Cavill in his full Superman attire in his archive, but he doesn't know when Warner Bros. plans to release this iconic image.

"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. 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. 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!' [laughs]."

When will we actually get to see the costumes in Batman Vs. Superman and the actors dressed in them? The director doesn't yet know exactly.

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"Unfortunately, I don't even know the timeline... Because the movie takes place so far from now, it's hard to know exactly. That all gets tied to marketing and strategies for the movie. It's not just a free-for-all, which I'd love it to be. Because I take a picture of the suit with my camera- I'm actually staring at one right now in my office. And it's just massive on my wall in my office and it's epic, let me tell you! And I'm like, 'God, I want to send this to the Internet immediately.' But I know I'm not allowed to [laughs]! I do value the sort of excitement of the way the film is [revealed]... the pieces that are released and sort of trickle out to everybody, and those reveals are exciting milestones for us."

CLICK HERE to read the full interview, where the director discusses Watchmen, Sucker Punch and much more.