'Supergirl': Nicole Maines on the Power of Playing the First Trans Superhero on TV (Exclusive)

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The 21-year-old transgender actress and activist talks to ET about playing Nia Nal, aka Dreamer.

Nicole Maines is writing her own history.

The transgender actress and activist made her anticipated debut as aspiring CatCo journalist Nia Nal, who becomes the superhero Dreamer, in the season four premiere of Supergirl, and the 21-year-old isn't shying away from the significance of playing the first trans superhero on television. Maines' groundbreaking casting was announced back in July.

“I’ve gotten to work with so many amazing people and I’ve gotten to hear firsthand how fans and audience members have reacted to seeing these storylines as these shows evolve and continue," Maines told ET at The CW's fall launch event on Sunday. "I watched the shows before I was even on them and I was like, ‘This is amazing. This is so empowering and validating to so many people,’ and now, I’m able to be a part of that."

"To get to give somebody the hope that we all desperately need right now -- that trans people can be superheroes, that trans people can be successful. They can thrive," she said.

Since joining Supergirl, it's been a whirlwind experience for Maines, who previously played a trans teen in Royal Pains, was featured in HBO's The Trans List documentary and was the subject of the 2015 book Becoming Nicole: The Transformation of an American Family. (Maines was the plaintiff in the landmark 2013 Maine Supreme Court case Doe v. Clenchy, which set the precedent for allowing transgender people to use the bathroom of their choice.) She credited her fellow castmates, namely Melissa Benoist, for helping guide her on her journey.

“Surreal is the word to use," Maines said of the past several months. "Everybody on set has been so welcoming and warm and inviting and supportive, and they’ve really embraced me as a member of the cast and let me know how happy they are to be able to bring the trans superhero to life with me.”

It's not lost on Maines that she'll now be the de-facto spokesperson kids and young adults will look to as TV's first trans superhero, territory she's more than qualified and comfortable being in. In reflecting on her own childhood, Maines admitted it would have been an asset to have someone who looked like her with similar life experiences to look up to on the small screen.

"Oh my gosh, I think that would have been validating, first of all. The soundbite I keep throwing out there is it would have been a game-changer because growing up, I didn’t have any superheroes who looked like me," Maines said, slightly overwhelmed at the idea. "If I had a trans superhero, it’s just… I can’t even imagine what… I can’t imagine. It’s so surreal to me now that we have one.”

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Maines' entrance as Nia on Supergirl was a memorable one. Running late on her first day at CatCo, the flustered cub reporter makes an unforgettable impression on Kat, who immediately sees similarities to her younger self and quickly takes Nia under her wing. In one poignant scene, Kara sits Nia down and tells the young journalist that she needs to not be afraid to "make waves."

“It starts out as a mentorship and it very quickly evolves into a really beautiful friendship -- between co-workers, between women, between reporters. And it’ll evolve into a beautiful friendship between superheroes," Maines teased. "All my scenes with Melissa are really, really fun because she’s sweet in person, so Kara and Nia have a really great energy together.”

“Kara really helps her come out of her shell and find her confidence and her footing in CatCo," she said, promising Supergirl fans that the evolution of their dynamic is "good." "I just love the relationship.”

Maines noted she has more similarities to Nia than she'd like to admit.

“She’s frazzled a lot of the time, which I really identify with," she said with a laugh. "I go on to set and I’m like, ‘What is happening?!’ She’s really dedicated to using her platform as a reporter to bring light to the issues that matter and I’m dedicated to using my platform as an advocate and as an actor to also bring light to issues that matter.”

But Maines is looking forward to expanding the Supergirl universe through the trans experience that Nia, and in due time, her superhero identity, Dreamer, provide.

“What’s important about having a trans character in shows like these is that we’re able to look at issues of goodness, justice and crime-fighting through a trans lens, which she also does with her being a woman and a reporter and a superhero. She’s able to bring a unique perspective to all of these issues," Maines eloquently said. "I can’t reveal too much, but in one of the episodes, she has a really, really, really great conversation where she is talking about the state of National City and she really uses her alliance as a trans woman to help people understand that.”

Supergirl airs Sundays at 8 p.m. ET/PT on The CW.