[Warning: This post contains spoilers from Monday's episode of Supergirl, "Human For a Day."]

It's also the secret that Hank Henshaw's (David Harewood) been hiding.

"It's the secret of Supergirl: within the body of the series of Supergirl, there is a Martian Manhunter series rolling throughout it," executive producer Andrew Kreisberg tells The Hollywood Reporter. "It's the thing that makes us giggle the most."

Back when the showrunners were on set to shoot the pilot, the idea to make DEO head Hank the Martian Manhunter was initially floated as a joke.

"[DC Comics CCO] Geoff Johns, [executive producer] Greg Berlanti and I were saying, 'It's so funny we cast David because he's got those weird ears. Like alien ears,'" Kreisberg says. "I don't remember which one of us said it, but it was like, 'If we were ever going to make a Martian Manhunter show, David would have been the perfect Martian Manhunter.' And Geoff said, 'Well, why can't he be?' We already had it set up that Hank was keeping this bad secret, and then we started thinking about well, what if it was a good secret? You think he's bad but then he turns out to be not only good, but the most good person in the DC universe."

Harewood had no idea he would be taking on such an important character when he first signed on for the role.

"I was told about two weeks into the job," Harewood says. "I knew something was changing but I wasn't absolutely sure what it was. The pilot was quite uncomfortable because a lot of what Hank said was exposition, so I was really pleased, because Martian Manhunter is such a huge character. It took me in a whole new, different direction. It was brilliant for me, because as much as I could, I couldn't really find an angle to play Hank Henshaw that was interesting before that. People are going to get to see a version of the Martian Manhunter that they've never seen before. There's some pretty emotional stuff to come."

But when the showrunners sat down with Harewood to tell him about his character's backstory, the sight of what John Jones looked like gave him pause. "Andrew gave me this model of a green Martian, and at first, I was a bit horrified," Harewood says. "I thought, 'I'm going to be playing Shrek for the next seven years.' I was anxious because I could see hours of prosthetic makeup and that was simply not something I wanted to do. But then I started reading it, and I was blown away."

Executive producer Ali Adler teases that John's abilities will blow Kara's out of the water. "He's got such tremendous powers," Adler says. "We really want to show off what he can do and we're definitely going to do that in upcoming episodes."

"There's a lot of fun to be had," Harewood adds. "He's a shape-shifter so he can be whoever he wants to be. So you'll find me being other members of the cast at some various points of the story."

But don't expect John to reveal himself to National City in the same, big way that Kara did as Supergirl. "In a way, John is closeted. He's afraid," Kreisberg says. "In an upcoming episode when Alex is actually encouraging him to use his powers, she says, 'What's the difference between you and Kara?' And he says, 'Your sister looks like a cheerleader and I look like a monster.' It's that soulfulness and that sadness, the one who is the most frightening-looking of all the Justice Leaguers and yet is the one with the purest heart." 

While he won't come out to the entire world just yet, having Kara and Alex finally know his secret identity will help Hank open up in ways he never thought possible on Earth.

"The revelation is as much a weight off his shoulders than anything. It's the fact that he can finally be himself," Harewood says. "And that, at times, can be very uncomfortable for him. I was wondering why he was being such a bitch to Kara. Kara's beautiful and attractive and blonde and gorgeous and I'm this seven-foot green Martian. As much as I just want to be myself, it would terrify people to be confronted with this alien. He's still got conflicts and issues that he has to deal with, but seeing Kara enjoy coming out of the closet or revealing her true nature, he's envious because he knows he can't quite do that."

But despite Hank's envy and fears, having his secret out in the open will actually bring him closer with both Kara and Alex. "Watching this relationship that's growing between him and Alex and him and Kara that started out in a very gruff place and then by the time you're getting into the meat of the season, they've become this little family unit," Kreisberg says. "He's become a surrogate father for them and at the same time, they're helping him become more human. It's one of the great surprises of the show."

Both Leigh and Harewood are most excited for viewers to see Hank's dynamic with Alex change in light of this revelation. "The Martian Manhunter, John Jones, definitely brings a lot of drama to the mix. It adds a lot of layers to the relationship between them," Leigh says. "He looks at her as if she's one of his own daughters. He had daughters and in a huge war, his whole family was eradicated."

"He promised her father he would protect her like his own child, and having lost his own child, Kara and Alex almost become his children," Harewood continues. "He loves them. Having lost his own children, he's got a lot of pain. He's got a lot of melancholy."

Viewers will get to see Hank's painful past first-hand when the show flashes back to his life on Mars. "In episode 11, we have a visitor from another planet who is a white Martian," Harewood says. "There are two Martian species, a green Martian species and a white Martian species. The white Martians are responsible for the death for the whole of the green Martians. There was a fire and they burned them. We'll get to see that and it's very emotional. Genocide, people being burned alive."

Original Article Source: The Hollywood Reporter