It’s safe to say that Wally West is one of the most beloved characters in the DC universe, where he’s been a mainstay since his comic book introduction as Kid Flash in 1959. Ever since the producers of “The Flash” announced that the speedster would be joining the show in Season 2, fans have been clamoring for a look at Barry Allen’s (Grant Gustin) comic book sidekick-turned-successor, who is portrayed in live-action by Nigerian-Australian actor Keiynan Lonsdale.

In the Dec. 8 midseason finale of “The Flash,” titled “Running to Stand Still,” Wally made his much-anticipated arrival in Central City — just in time for the holidays. Variety spoke to Lonsdale ahead of Wally’s debut to learn more about his iteration of the character, who was Iris West’s (Candice Patton) nephew in the comics but will be her brother — and Joe West’s (Jesse L. Martin) son — in the series.

Iris has had a little time to come to terms with the idea of having a brother, since she found out about Wally before Joe did. What is their dynamic like?

One thing I can say is Wally’s really into drag racing, which is not the ideal thing when your father is a detective and your sister’s a reporter. [Laughs.] So that’s going to cause some tension, and Iris, especially … she’s a fierce character so she’s pretty concerned over that, which kind of shows that she’s accepting him as a brother, really. It shows that the love is there, from both sides. From all sides, I think the love is there, but it goes to show that a lot more goes into creating a family than blood and love. It’s what you have to go through together.

For Wally, his walls are up pretty high. He’s quite defensive about who he is, what he does, and he doesn’t want a lot of those things to change, and doesn’t really believe that those things should be changed by newcomers in his life. Just because Joe is his dad, just because Iris is his big sister, doesn’t mean that he feels like they can control him in any way. So I think that’s going to be a pretty difficult dynamic for them to all overcome, but eventually, that will bring everyone together.

That theme of building a family with people who aren’t necessarily your blood is obviously a pivotal part of “The Flash,” since Barry is an adopted member of the West family. In all the ways that count, Joe has technically already had a son for many years, so how do Wally and Barry react to each other?

Well, Barry’s a good guy, and they’re all good people, but I think that that can sometimes be frustrating for Wally, because he’s trying to find his place in this family, but his place is almost already filled by this other son that Joe has.

So that’s another family member that Wally’s kind of forced to have, but Barry isn’t his blood, you know? And because Barry is such a nice guy, and a good guy, that can be even more frustrating for Wally. He doesn’t want to let a lot of people in, and … as cool as Barry is, Wally doesn’t want to let him in. So that creates this kind of cool little sibling rivalry, in a sense. At least from Wally’s point of view, without admitting it. I don’t think he would admit that to himself. It’s going to be quite funny.

What did the producers tell you about Wally as a character in terms of backstory or how to approach him when you got the role? Was there anything in particular you drew on?

It was kind of all in the script, to be honest, which is cool, and I guess because there are so many versions of Wally, there’s a lot of things I could pull from. Even more recently, I’m still learning more and more about Wally because the guys at DC just sent me a bunch of the old comics, which is really cool.

It’s just been a combination of things. It’s even the discussions that we had during the auditions, which really helped me as well … allowing me to go into the Wally that has his defenses up, that’s got quite a bit of attitude. Because deep down, especially when you’re growing up, you have your personality, and you are who you are, but usually it’s covered up by something else. And because of where he’s at in his life, and dealing with these things, he’s not going to reveal himself and let his guard down for new people. That was the main thing that we’re dealing with at the moment, which is cool for me because then it means as time goes on, I get to reveal more and more about his character.

And on top of meeting these new family members, which would be overwhelming enough after all these years, his mom is sick too, which must be its own unique kind of burden.

Totally, and that’s the right word, it is a burden. It’s tough what he’s having to deal with. I think as well, at that kind of age, you always feel like things are your fault in some way or another. It’s a tough life that he’s living at the moment, and rightfully so. If your mom is ill and you don’t know the rest of your family and now, all of a sudden, you are in a position where you have to get to know them… But he’s also old enough to make that choice himself: if he doesn’t want to , he doesn’t have to. It’s really a push and pull in his mind. His mom is ill and that just makes things very confusing.

Wally West was the first version of The Flash that I encountered, because of the “Justice League” animated series, and in a lot of iterations he’s portrayed as a very humorous, quippy and enthusiastic character. Have you had the opportunity to channel much of that, or because of the gravity of his circumstances, is he a little more reserved so far?

It’s a bit of both. I mean, he is serious and he is reserved and defensive and he has an attitude, but at the same time, he can switch things up with his humor, which is sometimes kind of dry. [Laughs.] I think that’s a big part of Wally, his humor, and obviously, more so in other versions where it’s more of a lighthearted kind of thing. I think that that could definitely be what comes out of it in the future, but while we’re dealing with these realistic, tough storylines with family, he is on the more serious side, although he’s still Wally, so there’s time for a joke, even if it’s not maybe the nicest timing.

What was your first day on set like?

When I got there, I’m pretty sure I got to meet everyone that day, which was really cool. Everyone was so welcoming. Everyone was really excited about me being there, which made me even more excited and more comfortable. The environment on set is super positive and happy and everyone chatting together, everyone joking, or rapping, or a couple of people dancing, you know what I mean? I was like, “okay, so this is my new job.” [Laughs.]

I’d imagine it must be especially intimidating to come into a show in the second season when everyone’s already established a rhythm?

Totally, and I seem to have a habit of this in my career. The first show that I did in Australia, I joined in the second season, and then with the “Divergent” series, I joined in the second film. Now with this, second season. It’s not an easy thing because you’re walking into a dynamic that already exists. People have already gone through stuff together, similar to a family, and you walk in as the new guy. It’s hard — even with everyone being welcoming, it’s still a difficult thing, but it certainly makes it easier. It allowed me to feel comfortable within my performance, and I felt supported straight away, so it was cool.

Mark Hamill also returned in this week’s episode as The Trickster — did you get to meet him?

I didn’t get to meet him, unfortunately. Here’s the thing — because I’m a fan of the show, I was like, “I don’t want to know what’s going on in the episode,” so I had no idea, because I was like, “well, Wally doesn’t need to know what’s going on. You only need to know what he needs to know.”

I think I’d only seen the first or second episode [of season two] on TV, and I was like, “I’m not ruining this for myself. I’m just going to know what I get to know and then we’ll go from there.” So Mark coming back to the show was a surprise to me! [Laughs.]

There’s a general lack of diversity among superheroes in TV and movies, especially when it comes to portraying heroes who aren’t white. How does it feel to get to tackle such an iconic character and know you’ll be a role model for a whole generation of new fans, many of whom probably won’t even know he was once a red-headed white kid?

Yeah, it’s amazing. It’s cool when you put it like that. It’s an interesting thing because, obviously, the traditional Wally West is Caucasian with red hair, and he had an iconic look, and people, because they fell in love with the character, also fall in love with the way that that character looks.

That was an interesting thing, seeing a lot of the discussions that people had about the real, live-action version of Wally being a mixed-race, African American guy, which I think is cool. It’s all part of the world reflecting itself. The world is a colorful place, so it may as well be the same thing in TV. For me it’s exciting. I just view myself as a human, so to be able to hopefully be a role model to African-American kids growing up, African-Australian kids growing up — because that’s who I am — and to kids of all races … I think as long as they can look at their screens and say “it doesn’t matter what I look like; I can be that, I can be a superhero, or I can be an actor,” I think that’s the important message to put out there. I love how they’ve done it with these shows, and with “The Flash,” they do it so organically with adding different cultures to the show, and people of color. I think they do it really well, and I think it works, and I think that’s why a lot of people tune into the show.

Wally is being introduced as a regular guy, but we all know that he has a heroic future to fulfill — have you been doing any training so that you’re prepared, just in case they decide to power you up?

I’ve been trying to run, although I haven’t been doing it this week. But I got here and I was like, “you know what, I should be running,” so I’ve been trying to run on the treadmill. I started doing yoga classes, randomly. I’ve only done three so far, but I’m like “whatever works” … and I also went to boxing the other day. I’m just trying to do a bunch of different things, because I don’t know when they could spring this up on me. I feel like with my luck, they’ll be like, “hey, so tomorrow you’re going be in the suit.” You never know. [Laughs.]

You mentioned that you were a fan of the show before you even auditioned to be part of it. What did you appreciate most about it, just as an audience member?

I love the structure of the show. I think it’s very positive, and it has a lot of energy to it, and it’s a consistent show, as well, which I think is important. I love the performances. I think all the actors are amazing — I think Grant, as Barry, you’re really rooting for him, and that’s such an important thing for a superhero, for your lead guy. You want to see him win, and that’s such a cool quality that he brings to the character, but he still makes him completely likable.

Also just the idea of family and making that the most important thing. Obviously, every TV series has their last episode, the thing for the audience to be waiting for until the end, and [in Season 1] we’re waiting for him to come face to face with the Reverse Flash, but what we were really waiting for was for him to make that decision about his mom — whether he got to save his mom, or whether he gets his dad out of prison. I think that’s such a cool, powerful thing, and they really did it well, so that’s what drew me to the show.

And now you actually get to be a part of it, which must make it even more satisfying?

Yeah, it’s a strange thing. I was just telling friends of mine, it’s weird now because before, when I got on set, I still saw them as the characters, but now I see everyone as who they are, just as people, because I’ve gotten to know them. [Laughs.] So I’m not sure which I prefer better, because I love getting to know everyone, but I got to have an illusion of everything, so it’s pretty funny being on a show that you’re a fan of.

This interview has been lightly edited and condensed for clarity.

“The Flash” airs Tuesdays at 8 p.m. on The CW.