On Monday's episode of Supergirl, the truth behind Hank Henshaw's (David Harewood) glowing red eyes was finally revealed . It turns out the head of the DEO is actually J'onn J'onzz, aka the Martian Manhunter and founding member of the Justice League.

The Martian Manhunter first encountered the real Hank Henshaw when he went on a rogue mission to capture the alien. Kara's dad Jeremiah Danvers (Dean Cain) died trying to save J'onn J'onzz, and the alien then took over Henshaw's body to run the DEO, save mankind and good aliens.

J'onzz revealed his powers and identity to Kara (Melissa Benoist) and Alex (Chyler Leigh) after an earthquake devastated National City and trapped him with Alex in the DEO.

David Harewood talks to TVGuide.com about the reveal and what it means for the series - including whether the Justice League is really possible.

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One of the Martian Manhunter's most notable accomplishments is founding the Justice League. Is it possible that's where Supergirl is heading?

David Harewood: That's really a question for Andrew [Kreisberg, executive producer.] I just get these scripts every week. Obviously, I would love for it to be heading in that direction. There is a wonderful moment in Episode 12 where I say to [Kara], "It would be great if you could come work for us full time."

There's a smidgen of, "Let's form a group." You think to yourself these guys are the Justice League. We've seen how successful The Avengers have been and just looking at the Batman v Supermantrailer, you've got Wonder Woman there. We are living in an age where DC characters are starting to come together. It's a very exciting prospect, but right now I just have to concentrate on the scripts that are infant of us and leave those decisions to the people that are paid far more than we are.

How soon after getting the part of Hank did you know that he was really the Martian Manhunter?

Harewood: Not until after the pilot. I came back to Hollywood in preparation for the series about two weeks before we started shooting. I didn't know then. I found out about a week into shooting the first episode.

I was delighted. My manager told me that they were changing my character, which I didn't understand. No one told me anything. I did all of Comic-Con without really knowing what was going on

Which Martian Manhunter comics did Andrew Kreisberg give you to read?

Harewood: The original ones by [Tom] Mandrake and [John] Ostrander. Their comic books were reportedly the best version of Martian Manhunter. Their original books were just fantastic. I have several copies of them. Lots of [Justice League of America] stuff which is just fantastic. Those were the first books I read, and I was just blown away by them.

Once you found out, how did that inform your playing Hank and his relationship with Alex and Kara?

Harewood: It gave me the missing link, actually. Shooting the pilot was a little uncomfortable for me for two reasons. First, it was a lot of exposition. This is the DEO. We do this and we do that. It was a little difficult to get any sort of characterization into Hank. I was struggling anyway because much of what is in the comic books is mainly cyborg Superman and not who Hank Henshaw was as a person. It was a missing link for me into getting much more depth and more three-dimensional characterization into what I was doing. I was starting as Hank.

[Knowing I was Martian Manhunter] gave me so much more to play. Then I could understand why he was so against Kara because he's almost trying to protect her. He didn't want her to put herself on the line. As Hank I kept searching for the reason why he didn't like aliens, why he was the way he was. I understood why he hated Superman but I couldn't find a reason for why he hated Kara so much.

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Knowing that J'onn J'onzz took Hank Henshaw's body, are we to assume that Jeremiah is really dead or is there a chance that we can see him have resurgence?

Harewood: I think he died, but whether or not Hank Henshaw is really dead, we don't know.

Now that Alex and Kara know who he really is, how is that going to change his relationship with the girls going forward?

Harewood: They still don't quite understand why I am choosing to hide my identity. We touch upon that in Episode 8. For Kara and Kal-El, her cousin, they were brought up on Earth. They look like humans. They can fit in very easily. J'onn J'onzz is all green and scary. If he wanted to be himself and live as J'onn J'onzz that's a terrifying thing because tall martians strike fear into the hearts of most men. He'd be forever hunted.

It's easy for Kara to say, "Be yourself," but it's much harder to live a life where you're consistently hunted and feared. That's part of the reason why J'onn continues to be Hank Henshaw. Also, as head of the DEO he's trying to use that as an organization that protects mankind and protects good aliens.

If he were to reveal himself, General Lane (Glenn Morshower) would get the DEO, and that's like giving Donald Trump the nuclear codes. It's crazy. The idea of keeping yourself hidden and your secret identity is not only one of self-protection but one of keeping the DEO out of the hands of those that would use it for detrimental reasons.

Speaking of General Lane, we already know there's tension between him and Hank. How will that continue now the audience knows who Hank really is?

Harewood: [J'onn] is very wary of General Lane because of his methods, strict views on aliens and on anything that is outside of the lines of ARMY thinking. He's too straight. He's too one dimensional for Hank/J'onn. J'onn is convinced that there are good aliens out there who mean to do good. He himself means to do good. Superman means to do good. Kara means to do good. These are not people who should be feared. These are people who should be embraced.

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How much of the Martian Manhunter's abilities are we going to get to see? Will he do some training with Kara?

Harewood: There's one sequence that comes up in Episode 10 where he tries to teach Kara how to fly, which is wonderful. He uses his abilities to investigate Maxwell Lord (Peter Facinelli) at one point. We do see him using his powers and see him using his strength and his shapeshifting. We have to remember it's not his show, so I think it will depend very much on the story line and how Andrew wants to develop it. I am just so delighted to get to be playing it.

If they did go in the Justice League direction, is there an iteration of the team that you would want? Who is your dream Justice League?

Harewood: I have to admit I grew up reading Stan Lee and Marvel. This has been a real journey for me in terms of rereading many of these comic books. Superman was more of an American thing so I didn't really read a lot of Superman comics growing up. A lot of the DC characters are still mysteries to me. I'd have to really sit down and look at the DC canon to see who is there.

There's the Flash of course, Green Lantern. There's a whole litany of characters that I'd love to work with.

Even if it's not the Justice League, does that mean you'd be in favor of a team up with The Flash or Arrow?

Harewood: Anything would be fun. Fans would be very, very excited but we're just beginning to find our feet as a whole anyway. Maybe down the line, but right now I'm really enjoying working with the people around me. We'll just have to see what happens in the future.

Supergirl airs Mondays at 8/7c on CBS.

(Full disclosure: TVGuide.com is owned by CBS)

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