This is an archived article that was published on sltrib.com in 2016, and information in the article may be outdated. It is provided only for personal research purposes and may not be reprinted.

When actors sign on to a TV series, they put a lot of faith in the writers. Those contracts generally commit actors for years, and they usually sign after seeing a single script.

"Supergirl" co-star David Harewood signed on to "Supergirl" to play Hank Henshaw, the head of the Department of Extra-Normal Operations — charged with protecting Earth against aliens. But Hank is really J'onn J'onzz — aka the Martian Manhunter.

"I didn't actually know at all that I was going to be playing J'onn J'onzz when I did the pilot," said Harewood.

Neither did the producers. It wasn't part of the plan when executive producer Greg Berlanti ("The Flash," "Arrow") and his team were launching "Supergirl."

"We had always known we wanted to do some twist with Hank, but we weren't sure about that twist," said Berlanti. And when he said aloud while filming the pilot that he wished Harewood had been cast as J'onn J'onzz, executive producer Geoff Johns — who is DC Entertainment's chief creative officer — said, "Why don't you?"

"And we realized — oh, that would be super cool and a nice twist on some of the things we've sort of done before," Berlanti said. "So people would go in with the presumption that [Hank] was a bad guy, and we'd actually be watching a hidden good guy underneath that."

For his part, Harewood was unsure how to play Hank and thrilled when told that Hank was actually a shape-shifter who had assumed the identity of a human. Producers didn't invent the character — J'onn J'onzz appeared in a comic book in 1955 and was one of the original members of the Justice League of America.

"They gave me this pile of comic books and a little model of J'onn J'onzz, and I went home that afternoon and read about eight hours' worth of comic books and was just blown away," Harewood said. "I thought this character had such an amazing backstory and amazing mythology.

"And I had no idea that he was so popular amongst the DC community. And also amongst the black community..."

Midway through the first season of "Supergirl" (Mondays, 7 p.m., CBS/Ch. 2), Harewood's role has already expanded greatly. The most recent episode, "Strange Visitor from Another Planet," focused on J'onn J'onzz's battle with a White Martian — a member of the race that murdered all the Green Martians, including J'onzz's wife and daughters. And an upcoming episode will flash back to J'onzz assuming the identity of Hank Henshaw.

"It's just been a great journey," Harewood said, "a really fantastic journey for me as an actor because there's just simply so much to play.

"I'm just absolutely delighted that this has landed in my lap."

Scott D. Pierce covers television for The Salt Lake Tribune . Email him at spierce@sltrib.com; follow him on Twitter @ScottDPierce.