When J'onn J'onzz returned to Earth from his trip to Mars, he wasn't alone: he brought back his father Myr'nn (Carl Lumbly), the only other surviving Green Martian. Now, J'onn -- known as both the Martian Manhunter and DEO director Hank Henshaw -- will have to adapt to a new way living. In "Wake Up," the next episode of Supergirl, both J'onn and Myr'nn will go through some growing pains as they adjust to their new life on Earth. During a set visit, J'onn himself David Harewood previewed the "bumpy road" of this father-son reunion and recounted some insight shared by Lumbly, who voiced Martian Manhunter in Justice League and Justice League Unlimited.

"It's been brilliant, working on the season so far, working with Carl [Lumbly]. He's such a lovely man, a great actor," Harewood shared. "He's also very familiar with the character, so it's a bit like just sitting around chatting about J'onn J'onzz all day. Like a J'onzz-off. He's such a great actor and he's a really nice man, and I've really enjoyed playing those things with him. I'm finding a lot of new colors with the character and I think you'll see in [tonight's] episode he has quite a major impact on my character. So yeah, I'm enjoying getting out of Hank's head and into -- he's kind of reminding me that I'm a 100 year old Martian and reminding me what I'm capable of so it's kind of fun."

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"Unfortunately, one of the episodes was a bit long, so they had to lose my storyline," he revealed. "But there was a slight conflict with Carl and me in that he fears that I'm kind of losing touch with my Martian heritage, and there's a little bit of conflict there. That even though I'm on Earth he just believes I'm becoming too detached from my Martian way of life. And I think that has an effect going forward because you know having got his father back he's very keen to get kind of to know him. But just like most relationships -- I find it in my relationships -- that even though you spend so much time apart, when you get back together it takes a while to find that groove, and I think that happens with Carl and me, J'onn and his father. They're taking a while for the two of them to kind of find their rhythm, but when they do I think it's going to be fun. So it's a bumpy road at first but I think they get there."

As to this week's episode, Harewood teased, "There's some highly comedic moments coming up where he's familiarizing himself with various Earth customs. Carl's great, I think he's a real... Carl's a favorite. We've had lots of guests and we've been very lucky with guests, but Carl's been great and everyone loves being around him, so he's very welcome. He's been a lot of fun."

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"I'm really enjoying playing this season with Carl because [J'onn] is not the last green. There's another green but that green is his father who knows him very, very well. There's some nice nuances between me and him that come out and hopefully stay in because it's been really, really fun working with him and just seeing how different his approach to the work is," he added.

"It made me go back to reading the comics. You know he's been Hank Henshaw now for 50 odd years or 30 odd years and I think he's got slightly caught up in that one identity, and he's used to having hundreds of identities. I think his father reminds him that he's perhaps gotten a little too caught up in the one identity," he explained. "What's been nice to play has been this sudden awakening in J'onn that his father creates. That it's not all about the DEO, life's not all about protecting the Earth from external forces, there are other superheroes who can do that. I just get the impression that J'onn -- from where I left him the last time -- that he's just realizing how."

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"In fact, it was Carl who told me this in the last episode. When he played Martian Manhunter, the Martian Manhunter decided to give it all up and go and marry an Asian lady and go and live in, you know, the Philippines or something as a normal person because that's what he finds interesting. He doesn't find all these things of saving the world or fighting aliens, you know, just loving somebody, I think that's the kind of character J'onn J'onzz is -- and that's why I like playing him -- is that he has other interests," he continued. "What I'm gathering from the scenes with Carl is that he's kind of remembering this about himself. 'Why have I been Hank Henshaw for the last 50 years? There are other things in life I can do.' So that's what I think he's been exploring."

Asked which comic book storylines inspired him for this storyline, he said, "I really like the Ostrander Martian Manhunter series, brilliant book. There's a couple of stories in there, there's things that stick out. Where he says he trained as a philosopher as well as a manhunter, and that he's always looking at both sides of the argument. That's what I'm saying is he's just slightly gotten into always looking one way. And having his father remind him of his heritage, it's kind of enabled J'onn to take a step back and be a bit more relaxed about life and maybe a bit more philosophical about things, and hopefully that can play out in some of the scripts."

Airing Mondays at 8 p.m. ET/PT on The CW, Supergirl stars Melissa Benoist as the Girl of Steel, David Harewood as Martian Manhunter, Mehcad Brooks as Jimmy Olsen, Chyler Leigh as Alex Danvers and Jeremy Jordan as Winn Schott, with appearances by Calista Flockhart as Cat Grant and Tyler Hoechlin as Superman.