Most little kids play dress-up to pretend they’re someone else, but Nicole Maines played dress-up so she could be herself.

“My brother Jonas and I were always pretending to be in ‘The Wizard of Oz’ or something,” said Maines, 21, who was born a boy but identified as a girl from toddlerhood. “I loved it because I could wear the kind of clothes I was truly comfortable in. People would say, ‘Oh, she’s just playing dress-up,’ but it was much more to me.”

Maines, who won a landmark court case for transgender rights in 2014, went from acting out movies and plays with her brother to theater productions at Orono Middle School. On Sunday, she will become TV’s first transgender superhero when she makes her debut on The CW Network’s family action show “Supergirl.” She’s one of only a dozen or so transgender performers currently playing transgender characters on series television. Her character, Nia Nal, is a crime-fighting reporter, also known as the superhero Dreamer. Her power is seeing into the future.

After decades of being portrayed in film and TV, largely as seamy characters, transgender men and women are hailing Maines’ role as a potential catalyst for more positive portrayals in media and more work for transgender actors. Activists say Maines’ role, and life story, are especially inspiring to transgender youths as they struggle for acceptance at school, from parents and in the world in general.

“It’s critical that we tell stories about trans youth in mainstream pop culture, and casting Nicole Maines as TV’s first trans superhero is an important step in the right direction,” said Nick Adams, director of transgender media and representation for GLAAD (formerly the Gay & Lesbian Alliance Against Defamation), a group that monitors the portrayals of gay, lesbian, and transgender people in the media. “Nicole and her family have already changed the society for the better, and now more young people will learn about their fight for full equality for trans students.”

Alice Staples, a 17-year-old transgender girl from Hollis, did a school project on Maines and her court battle. She thinks that Maines’ role on “Supergirl” combined with her personal story will definitely have a positive impact on public opinion.

“It’ll help spread awareness and show trans people are not perverted, they’re normal, they can even be heroes,” said Alice, a senior at Baxter Academy for Technology and Science in Portland. “I’m still in the learning process myself, and one of the first people I turn to for answers is Nicole and her story.”

NOT A PERFECT TRANS PERSON

Maines says she can identify with her character on the show because she “looks at what’s wrong and does what she can to fix it. Nia Nal is passionate about using whatever platform she has to effect change.” So is Maines.

Born a boy and named Wyatt, Maines was not yet 3 when she told her parents she hated having a penis and asked when she’d become a girl. After several years, Maines’ parents decided to let her live as a girl and had her name legally changed to Nicole.

Her family had lived near New York’s Adirondack Mountains, in the town of Northville, until Maines was about 5 years old. Then they moved to Orono and later, to Portland, where Maines attended Waynflete School.

In 2007, Maines was in elementary school, at Asa Adams School in Orono, when she became the focus of what would be a groundbreaking lawsuit over transgender rights. The school had stopped her from using the girls’ bathroom, after a complaint from another student’s guardian. The suit made its way to the Maine Supreme Judicial Court, which ruled in 2014 that her rights had been violated. It was the first time a state supreme court had affirmed a transgender person’s right to equal access to bathrooms in public places.

Maines has spent a lot of time since then working to raise awareness about the issues facing transgender people – those who identify with a gender different from the sex they were born with. Her story was detailed in the 2015 book “Becoming Nicole” by Pulitzer Prize-winning journalist Amy Ellis Nutt, and she was one of 11 transgender Americans profiled in the 2016 HBO documentary “The Trans List.”

When she was a freshman at Waynflete School in Portland, Maines testified before the state Legislature against a bill that would have required people to use public bathrooms that corresponded to the sex they were born with, not the gender they identify with. Her father, Wayne Maines, said he told his daughter she didn’t have to do it because it would mean telling the whole world who she is. But she did. The bill was eventually killed. This role on “Supergirl” is an extension of Maines’ activism.

“I want to portray her honestly, in a way that’s accessible,” said Maines, during a phone interview last week from Vancouver, British Columbia, where “Supergirl” is filming. “I don’t want her to be this perfect trans character. When there were fewer on TV, they had to be perfect. But I think Nia can be flawed, she can have her own struggles. She doesn’t need to be a perfect trans person, she can be a real trans person.”

TRANSGENDER CASTING IN TV AND FILMS

An estimated 1.4 million people – around 0.6 percent of U.S. adults – identify as transgender, according to a 2015 study by the Williams Institute at the UCLA School of Law. While some people undergo hormone treatments and surgery so that their bodies match their gender identity, not all do. Maines underwent sex-reassignment surgery before entering college.

Maines’ role on “Supergirl” was announced less than two weeks after actress Scarlett Johansson withdrew from a planned film called “Rub & Tug,” following a backlash of protest. Johansson had been cast to play a transgender man in the upcoming film, the true story of Tex Gill, who ran a prostitution ring in the 1970s and ’80s.

Transgender activists argued that Hollywood had given plum transgender film roles to non-transgender actors for too long, denying people of work and their right to tell their own story. Several actors have won Oscars for transgender roles, including Jared Leto for playing a transgender woman in “Dallas Buyers Club” (2013) and Hilary Swank for playing a transgender man in “Boys Don’t Cry” (1999).

But while Hollywood has been slow to have a transgender actor in a big-budget film (because they feel they need a bankable star, critics say), TV has had a slow and steady increase in transgender characters in the last decade or so.

During the 2017-18 TV season, there were 13 transgender men and women as characters on series, according to GLAAD’s annual report of LGBTQ inclusion on TV. There were also four non-binary characters, meaning people who do not fully identify with either gender. The total of the two categories, 17 characters, made up about 5 percent of all characters on broadcast, cable and streaming TV series. In the 2015-16 season, there were seven transgender characters.

Shows like “Grey’s Anatomy” on ABC, “Star” on Fox and “Orange is the New Black” on Netflix all have transgender characters played by transgender actors. The show “Transparent” on Amazon stars actor Jeffrey Tambor as a transgender woman, which he is not, but several series regulars are transgender actors. Comedian Ian Harvie, a transgender man originally from Maine, has played a recurring character on “Transparent.”

He thinks Maines’ role on “Supergirl” will reach a young audience, since it’s more of a family show than some of the others listed above. Because Maines is young and has grown up at a time when transgender issues are much more publicly discussed than a decade ago, her portrayal and her activism could have a powerful effect on transgender youth.

“I’m excited about what her getting this role will do for other transgender girls who didn’t believe people like them existed,” said Harvie, who grew up in Bridgton and Topsham. “In grade school and junior high, and in general, being trans is not exactly safe or welcomed. People will see someone like them thriving and say, ‘I can have a life, people will love me.’ ”

A PASSION FOR TELLING STORIES

Maines graduated from Waynflete School in 2015 and later enrolled at the University of Maine in Orono. But she had always loved acting. Her father recalled Nicole and her brother acting out just about every movie and TV show they saw. Maines said her love of acting really took off at Orono Middle School, and she has fond memories of playing the fussy Veruca Salt in “Charlie and the Chocolate Factory” opposite her brother Jonas as Charlie. Her lifelong love of acting and storytelling convinced her to pursue acting full time during the last couple of years.

“I remember in high school trying to figure out what I wanted to do with my life,” said Maines. “And I thought about the idea that, if you do what you love, you’ll never work a day in your life. I’ve always loved acting and watching behind-the-scenes looks at shows and films. I thought it would be incredible to be a part of that.”

She started auditioning for parts. This past spring, the producers of “Supergirl” put out a casting notice for a transgender actor to play a transgender role in the upcoming fourth season. In the casting call, producers said they were looking for a transgender woman in her 20s to play Nia Nal.

The show is based on the DC Comics character Supergirl, who escaped the doomed planet Krypton like her cousin, Superman, and was sent to Earth. As Kara Danvers, she uses her powers for good and works as a reporter at CatCo Worldwide Media.

And this season, one of the new reporters happens to also have superpowers – Nia Nal, played by Maines.

When Maines heard about the part of Nia Nal, she made a film of herself reading the part and sent it to “Supergirl.” Soon thereafter, she went to Los Angeles to act in an indie film called “Bit,” playing a transgender teenager trying to fit in with and understand a group of feminist vampires. While in Los Angeles, the producers of “Supergirl” asked to see her in person. She went and, a day later, got the part. Then, in July, the show announced Maines had been cast.

A CW news release says that Maines’ character is a reporter who “tries to use the power of the press to shine a light on the issues which threaten to tear the city apart.”

Maines said the cast of the show, which stars Melissa Benoist in the title role, have been “incredibly welcoming” and helpful during the first month or so of filming. Actress Katie McGrath, who plays Lena Luthor, asked Maines to lunch her very first day on set in Vancouver to make sure she was settling in OK.

Since getting the role on “Supergirl,” Maines has been giving interviews to magazines and TV shows, talking about the show and about growing up transgender. Immediately after the phone interview for this story Monday, she filmed a wide-ranging interview with Ellen DeGeneres for her talk show, “Ellen.”

Maines still has a little bit of a hard time believing the position she’s now in and the platform she has.

“Every day, I feel like I tricked somebody to get here, like I slipped in under the velvet rope or something,” said Maines. “I can’t believe I get to do this as my job.”