SPOILER ALERT: Do not read if you have not watched “Bottle Up and Explode!,” the fifth episode of “Grey’s Anatomy” Season 18.

When E.R. Fightmaster landed the role of Dr. Kai Bartley on “Grey’s Anatomy,” the show’s first non-binary doctor in its 18-season run, they knew one person in particular would be excited.

“I used to watch some of the episodes with my mom, [who] religiously watches the show,” Fightmaster, who is also non-binary, tells Variety. “And it’s funny, because I have done other things, but when I told my mom about this, this is the first time she actually freaked out. Which, of course, made me feel very good. My relationship with show is through my mother and I think hearing her freak out was was the first time that I allowed myself to really think, ‘Oh, yeah, this is an institution.’”

Fightmaster’s Kai joined the series via the medical drama’s Minnesota-set storyline, as Meredith (Ellen Pompeo) and Amelia (Caterina Scorsone) came aboard part-time to join a research team that is working to cure Parkinson’s — on the behalf of Dr. David Hamilton (Peter Gallagher), who is both funding the project and has the disease.

Even though they have joined a very established series, Fightmaster says it has been an easy set to step onto.

“The family that you see on ‘Grey’s Anatomy,’ that is very authentic,” Fightmaster says. “I have really felt that I am getting to be a part of something special. And when I watch shows, I always hope that they have the dynamic that I’m seeing, that they have this closeness that I’m witnessing. And I can tell the audience that for ‘Grey’s,’ that is real.”

Here, Fightmaster talks to Variety about portraying the medical drama’s first non-binary doctor, the possible blossoming romance with Kai and Amelia and the how the research team may handle challenges with Dr. Hamilton.

What does it mean to you to portray the first non-binary doctor on the show?

It is an honor. It’s really exciting for me. I see a lot of the entertainment world through my eyes as a child, and I think about how little representation I saw on TV. And when I was growing up, that led me to not knowing that I was gay for a long time. Not having the language or understanding that I was gay. Not really being able to see a lot of people who presented gender in different ways than the norm. Being able to become some kind of representation for non-binary people — of course, I don’t represent every shade of non-binary, but I represent mine — and being able to be that on screen, for whoever needs it, is really, really rewarding.

What conversations have you had with the writers and what input have you had in crafting Kai so far?

I bring myself to the character, but I will say that the “Grey’s” writers do not need a lot of help. Because they have such a legacy of diversity on the show, they have been very well-versed in writing full characters, full people that have their diversity, but are also human beings. And so, the way that my character has been handled thus far, even the first scene that I’m in, I am referred to as “they” and it’s not a big discussion. It’s not a big debate. It’s just that I am established as a non-binary person and we move forward. That meant a lot to me, and showed me that the writers were going to be able to treat this character with the amount of respect I could possibly hope for.

Was that something you saw from the initial audition sides, or was it something that became more clear when you got your first script?

I think, in my memory, the character itself was non-binary. That’s all the writers. But what I think the writers also do really well on this show is they create these characters that aren’t vague, but are almost simple enough that when they bring actors onto the show, you can infuse your personality into them. So when I read the script, it was very easy to see the way that I would behave if I were Kai, how I would flirt if I were Kai. The only unbelievable thing is that I could possibly do science.

How has it been adjusting to the medical jargon?

[Laughs.] You think that you’ve memorized a line, and then you get on stage and you realize that you have been practicing the word incorrectly in your home for about four days. And then every take you do, you’re just mispronouncing that word. So that’s the reality that I’m currently dealing with. But I like to think that I’m getting better at it.

In “Bottle Up and Explode!,” Kai was very intrigued by Amelia’s history and present romantic status. What is their take on her?

They don’t seem displeased. [Laughs.] I think that there’s a very obvious flirtation there. It’s not out of the realm of my personality to look at a woman who is good at her job, handling equipment, speaking in medical jargon — I, as an actor, would be attracted to that. So I’m sure that Kai feels the same way.

Amelia tells Kai about her complicated relationship with Link (Chris Carmack) and their child. Do any of those ties elsewhere give Kai pause?

I think of Kai as a very grounded person. And I don’t think that someone having a fraught past relationship would get in their way.

Something that excites me about the Kai and Amelia plotline, at this point, is that there seems to be a lot of tenderness there. And respect. And so, if Amelia is coming out of a relationship that is heterosexual and that was bound for marriage and has children involved, I think it’s really interesting to think about allowing that character to enjoy life after that, without judgment.

Whether it’s with Amelia or someone else, what does getting to portray Kai in a hypothetical love story mean to you?

I think it’s really important for people not only to see themselves on-screen, but to see themselves in different versions of humanity on screen — whether that is being a scientist or fully in love. And I don’t take it lightly in any way that I get to be a non-binary person that I have not seen on-screen in this show. Getting to see someone be non-binary and flirting and doing science and communicating — it’s all these baseline things I think a lot of times we can take for granted with people that are cis. We don’t see a lot of non-binary representation, but actually it really is important to see a non-binary person from every angle. If [it happens], to get to be allowed to be a love interest is a very important thing to see.

The episode also included the tidbit that Kai knew Tom Koracick (Greg Germann), who briefly joined the Minnesota hospital team — but wasn’t a fan. What conversations did you have with Greg about your characters’ potential shared history?

Unfortunately, for me as an actor, it was a pain in the ass to pretend to not like Tom in any way because Greg Germann is incredible. And it’s me, Peter Gallagher, Caterina Scorsone, Ellen and Greg in a green room in between the scenes, and he is just consistently making me laugh in a way that felt so familiar to me. I felt that when the day ended, “OK today I acted because pretending to not like this man is the hardest thing I’ve ever had to do.”

Looking ahead, what can you preview about the team’s dynamic as they try to find a cure for Parkinson’s?

It’s really been fun as an actor, and even a viewer, to look at the four of them find their groove and to find a way that they actually, naturally, interact. Because every person — every actor, and every character — in that room does bring a very different energy. And I think that’s what makes the scenes so dynamic and fun for me. The minute that they yell cut, it really is this special room. Any room is special with Peter and Ellen and Caterina inside of it, but the hardest part is for us to settle down and get back to shooting, because I genuinely believe that we are having a really fun time together.

What will be the biggest challenge for them as they navigate the natural ups and downs of research?

It seems to me that the biggest hurdle here is Dr. Hamilton’s insane ego. We are trying to fix Parkinson’s for him, but it’s also through his funding, [which] creates a really interesting dynamic. And I think it’ll be really interesting to see it plays, when someone is personally funding something, how involved they are and how strategic you have to be when you are both being paid by them, but you are trying to reach the same goal that they are.

As his disease progresses, how will that impact both the urgency of the team and also potentially his limitations to assist?

It’s been interesting to get to act with Peter Gallagher, because he is so fun and warm, and he’s so effervescent. And so even having these written conversations in this world where he is losing mental capabilities, losing physical capability, does make me think about Parkinson’s in a different way. I’m really lucky to not have a lot of people in my life that are affected by that disease, but I hope that the people who watch the show that do have loved ones that are affected by Parkinson’s feel that the show is handling it with as much respect and care as it deserves.

“Grey’s Anatomy” airs Thursdays at 9 p.m. on ABC.