Season 1 of The Umbrella Academy landed on Netflix Friday, so viewers may know by now that the show features one of the strangest families ever put on TV. The seven Hargreeves siblings were all born on the same day in 1989 as part of some unexplained supernatural event — none of their mothers had even been pregnant when the day began! There were other children born that day too, bur Sir Reginald Hargreeves (Colm Feore) adopted these seven because of their unusual abilities, hoping to mold them into a superhero team capable of protecting the world. But even amid a family of mediums and superstrong warriors, Number Five (Aidan Gallagher) stands out.

While his siblings have both numeral designations and normal human names like Luther (Tom Hopper) and Klaus (Robert Sheehan), Number Five has no other name. On top of that, he has the ability to travel through both space and time, meaning he can teleport himself across a room or catapult himself into the future. This has separated him from his siblings in multiple ways.

As a child testing his powers, Five accidentally threw himself too far into the future and spent decades trapped in a post-apocalyptic wasteland. Eventually he figured out how to go back in time to try and help his siblings stop the apocalypse from ever happening, but he’s now in the unique situation of possessing the life experience of a 58-year-old man in the body of a teenage boy. That made the character particularly difficult to cast, according to showrunner Steve Blackman.

“When it came to Number Five, I started to panic at one point, because I’d literally seen hundreds of kids with Peter Hoare, the director,” Blackman tells EW. “Then I got a tape from Aidan Gallagher, who looked at the camera and said, ‘I would kill to have this part,’ and then launched into his audition. I just instantly knew, that’s Five. He had a little bit of this brooding sullenness which he needed to do, but he also could bring the complexity of being a 58-year-old man in a 13-year-old’s body. Aidan was such a professional on set. You don’t often see younger actors who can be around five 30-year-olds and not flinch, but Aidan could. He’d come to set every day, sit in the room with these other actors, hit his mark, hit his lines, and never screw up. He just brought that brooding anger and gruffness that had to be Five. I felt very blessed that we found Aidan because at one point we worried, ‘Oh my God, we’re not gonna find this kid.’”

For his part, Gallagher says the key to understanding Five is his sense of alienation from the other characters. Hargreeves’ death brings the family together again for the first time in years, which unearths all kinds of history and differences. But while his siblings are focused on that, Five only cares about stopping the impending apocalypse.

“When I key into the character of Five, I’m generally drawing upon a mental state — not so much thinking about the 58-year-old side of him, just the way he reacts to things. For me, that’s really the key to how he interacts with other characters,” Gallagher tells EW. “Five has sort of had his own little life aside from everyone. He spent 45 years in the apocalypse, and that took a toll on him and was a big part of his overall trauma. That was one of the most interesting things about Five that I got to play. That’s one of the things that separates him and the family apart, because of how much he knows, and how much they’re oblivious to. He definitely has a different relationship with the pacing of the series than the others do. They’re more relaxed, they’re dealing with the death of Hargreeves, and Five isn’t really concerned with any of that. He’s more worried about the incoming apocalypse, and he has no clue as to what caused it.”

Almost no humans were left in the aftermath of the apocalypse, so Five had to turn to some drastic measures in order to not lose his mind. In one of the series’ most absurd touches, Five’s emotional anchor became a mannequin named Dolores, which he carted around, looked after, and talked to as if it were a real person. Even as he’s racing to stop the apocalypse in the present day, Five is also desperate to reconnect with Dolores.

“It was definitely one of the things I looked forward to because I had a feeling they might expand on it, and I wanted to play around with how his trauma would affect the relationship between the two of them,” Gallagher says. “If I were to do a scene with her, I would make dialogue for her. He would be having a real interaction with her, a real conversation, and for that he needs a real character. So Five is playing the part of Dolores. That is a fun dynamic that I was definitely looking forward to shooting.”

Not everyone involved in The Umbrella Academy show was familiar with the original comics by Gerard Way and Gabriel Bá, but Gallagher was. As a result, he says, one of the highlights of working on the show was getting compliments from Way on his interpretation of the character.

“He said, ‘You got it, man. Great job,’” Gallagher recalls. “For me that was the ultimate reassurance, as a fan of My Chemical Romance and the comics, that at least in the creator’s mind I was doing this thing justice. I think one of the earliest moments with that was right after my first scene with Ellen Page, right on the first day. That was when it happened. He pulled me aside and we talked for a moment.”

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