Tonight, "iZombie" will crossover with "Supergirl" -- sort of. In "Ace Reporter," the next episode of "Supergirl," "iZombie" star Rahul Kohli will guest star as Lena Luthor's old flame Jack Spheer and his arrival in National City will certainly heat things up for the Girl of Steel. As it were, Spheer is in town to debut his miraculous new nanotech, but his invention -- and Lena's involvement with him -- pulls Kara into an investigation she never expected.

Speaking with CBR, Kohli introduced his version of Spheer, who may look a little different than his comic book counterpart when he shows up on "Supergirl." Kohli also filled us in on how his character differs from the comics, why he wants to steal Katie McGrath for "iZombie," what caught him off guard when he arrived on set and more.

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CBR: As I'm sure you know, Jack Spheer is also a character in the comics. Did you do any research to prepare for the role?

Rahul Kohli: I did! And I saw that he was a giant gas, and I wasn't sure how to prepare for that and what I would need to do, but then I found out very quickly that we are actually doing a different spin on that character, which is not necessarily what the fans may have read in the comic books. This is a new take on the character for the "Supergirl" universe.

Because this is a new version of Spheer, did you have the flexibility to add your own spin to the character?

Oh yeah! Absolutely! I mean, there was a lot of freedom with that. Initially, I thought I would have to do an America accent, but that wasn't required. They were happy to have a British accent. In terms of his look, they had the idea that they wanted not a Steve Jobs-type, but the tech genius guys that do the keynotes and pep talks; they wanted that kind of energy from him. The only thing I kind of clung onto was I insisted that he should have a beard, which is my acting clutch. I need half my face covered with hair, it seems, to feel comfortable on camera.

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Can you describe Spheer's personality in three words?

He's a charismatic tech genius back in National City to debut this new technology that he's been working on called Biomax, and it's microscopic nanobots that are able to heal injuries and cure diseases. He's also an old flame of Lena's.

If you could tease only one thing about Lena and Spheer's relationship, what would be?

Things move very quickly for them. There's no real messing around with those two characters. There isn't a lot of procrastinating about how they feel towards one another. They're like a charged couple.

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What was it like to work with Katie McGrath?

Oh, she was awesome! I think Katie kind of set the tone for the rest of the episode… Our first scene was actually quite an intense relationship scene to do at 7 or 6 in the morning. That was my first day meeting Katie, and then we had to do certain things that are not necessarily comfortable for new people to do, but she was incredible and I tried desperately to steal her for "iZombie" but I think "Supergirl" beat me to it with the old "making her a season regular." Now we can't steal her!

There's a lot of anti-alien prejudice going on in Supergirl's world right now. Will we see what side of that line Spheer falls on?

No, we don't. No, the world and the universe that they've created within "Supergirl" is kind of suspended for this storyline. It's a highly contained story within that arc, if that makes sense. It's all about him sliding into that world. It's more about how he affects everyone else's day-to-day routine.

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So would you say the episode is more of a character piece?

Yeah! It's just its own special kind of Jack episode, where he comes and messes everything up and has Lena in a tizzy and Kara investigating him. Yeah, you don't get to see Jack interacting with many of the characters or giving any of his opinions of the goings-on in National City.

On "iZombie," you play a character with a heart of gold. What was it like for you to take on Spheer, who seems to be a bit shadier?

It's great! I mean, Jack… I think he's been pitched -- and rightly so -- as some sort of villain of the week, in that format, but that actually is kind of misinformation. He's not as mustache-twirly as people would think he's going to be. It's a lot more layered. [Ravi and Jack] are actually still quite good people, and both charming in their own way. I think the biggest difference between the two is Jack's not funny. I don't think I had a single joke, whereas Ravi is much more of this comedic ball of energy in "iZombie," so it was interesting… because that's what I do on "iZombie." If I get nervous or if don't know what to do in a scene, I resort to a stupid face. That seems to have worked the last three years, but with "Supergirl," I have to do something different to feel comfortable.

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As a big comic book fan, what was it like for you to step onto the set and become part of Supergirl's world?

It was awesome! I mean, it's not like they had a Batmobile that I could sit in. Much of the scenes that I was in were just real-world type locations, like restaurants and offices, but I did, like on my first say, cross paths with Melissa [Benoist] when she was dressed as Supergirl and honestly I reacted like a five-year-old. She just stopped me in my tracks. It's so iconic -- you know, the symbol and the cape. Melissa just looks phenomenal as Supergirl. It was an unexpected hit! I wasn't expecting it to be a freak out. Like if I was cast in "Star Wars," I know in ten seconds I'm going to scream about a Stormtrooper or the Millennium Falcon, whereas on "Supergirl" I was just excited to try a new character, but it caught me off guard. I really did freak out when I saw Melissa dressed as Supergirl.

"Supergirl" has a pretty big ensemble cast. Do you have a favorite moment or experience on set?

Yeah! I'll tell you what caught me off guard was Chris Wood. He and ["iZombie" star Robert] Buckley are like the same person on different shows. They have the same sense of humor and joke delivery. He just had me in stitches. They have a lot more freedom. Us, being a comedy, we don't realize improvise it. [Co-creator] Rob Thomas and the writers do such a great job of the jokes. We don't chip in with improv at all. We pretty much stick to what's been written on "iZombie." What caught me off guard on "Supergirl" was that there's a lot more freedom to experiment, and Chris definitely takes advantage of that. We did a scene where every time Chris came up with something funnier than the last line, and it was unexpected. I wasn't expecting it to be that kind of gig, but it was. It was hilarious.

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Though the odds of this happening are slim, what would you like to see in a "Supergirl"/"iZombie" crossover?

I'd want Ravi and Lena to start dating! [laughs] I had such a great time working with Katie. She was fantastic, and -- like I said before -- I tried to steal her. So if I can't steal her, then, have my character and her character come out across worlds, that'd be awesome.

Starring Melissa Benoist as the Girl of Steel, "Supergirl" airs Mondays at 8 pm ET/PT on The CW. The series also stars Mehcad Brooks as Jimmy Olsen, Chyler Leigh as Alex Danvers, Jeremy Jordan as Winn Schott, David Harewood as Martian Manhunter and Chris Wood as Mon-El.