Sebastian Stan was “losing sleep” over not resembling Donald Trump physically.

“This was always a problem. Everyone has been saying to me: ‘You don’t look like him.’ You’ve already seen so much of him, so I thought it would be better to go ‘less is more’. But we still had to find the right hair and make-up people,” he said at Zurich Film Festival.

“When we started the film, we had a prosthetic test and it really didn’t look like him at all. I was very worried about that – we all were. Then fortunately I called the team who helped me with [portraying] Tommy Lee on ‘Pam & Tommy.’ We were able to find the right balance.”

Since its Cannes premiere, Ali Abbasi’s “The Apprentice” has been sparking controversy due to a scene which shows Trump sexually assaulting his then-wife, Ivana.

“You have to look at your feelings towards something you’re about to do and you have to be very diligent, strict and honest with yourself. Which of them are going to work for you and which are going to work against you? The ones that are going to work against you, you have to discard in order to serve the story,” said Stan about the violent sequence.

“It’s interesting to listen to Ali talk about that scene, because he goes: ‘Why is it controversial?!’ You can’t ignore [Ivana’s divorce] deposition, when she went on record to explain it graphically. Then she retracted it. Screenwriters had to decide what’s closer to the truth and maybe speaking under oath is closer to the truth. You can’t tell this story without including that part of their relationship and that part of his character.”

When he first read the script, written by Gabriel Sherman and depicting Trump’s friendship with infamous attorney Roy Cohn, Stan went as far as “crossing out the names of the characters.”

“I had very strong feelings about it. Then I did this game with myself and I could see a little bit clearer once I removed that big stain from the windshield. There was a story there about someone who started out a certain way, had very specific ideas and dreams, fears, insecurities and family issues, and then something happened. The man, to me, lost the person he was.”

He added: “It seems to me that [in Trump’s case] the need for power and control is so deep it overpowers any other need. I think we are talking about someone who has made the decision that ‘No one will ever have more power than me, ever again.’ You have to ask yourself if a person like that can really make the right decisions. If you are calling yourself the leader of the free world, we have a right to question that.”

As the team kept on working, trying to explore the very idea of the “American Dream” and the hero complex, said Stan – “This obsession with being all you can be, being the best of the best at everything” – Ali Abbasi’s unique perspective turned into an asset.

“He’s not American and doesn’t play for any team. I thought: If anyone has anything to say that we’re not thinking of, being so deep in it, it’s probably someone not from America.”

He also opened up about working with Jeremy Strong, cast as Cohn.

“Roy Cohn was the devil. A lot of people say that,” he noted.

“I’ve always admired [Jeremy] because I felt he cares. Everyone says they care, but they do only as long as it serves their interest. We met a month and a half before shooting: I was trying to gain weight and he was losing it. He said: ‘Do you want to eat anything?’ ‘Yes, I’ll have a burger with fries.’ He replied: ‘I’ll order a cocktail.’ I said: ‘I don’t drink now, he doesn’t.’ He said: ‘Yeah, but he drinks with me in the movie,’” laughed Stan.

“I didn’t really see Jeremy out of character. We would only meet on set, as Roy and Donald. There was no time for dinners or hanging out, or anything like that. I think it helped.”

Playing someone “everyone feels very strongly about and we can’t escape” was especially difficult, but playing a real-life person is a “technical process similar to learning how to play an instrument,” said the actor.

“You are sitting there, every day, for a number of hours. It’s slow and tiresome and annoying, and then you get faster [at it]. You know what the goal is, you just have to get there somehow. I always think of ‘Apollo 13,’” he said, recalling the “putting a square peg in a round hole” scene. “You have to figure out how to fit into it even though you’re not that.”

While “The Apprentice” is very much on his mind, Stan also discussed his role as Bucky Barnes in the Marvel universe.

“Action movies are really fucking hard. I think they don’t get enough recognition. Tom Cruise is not a normal person, right? I don’t know how he’s doing what he’s doing. I’ve never thought I’ll get to play the same role for 15 years. It’s weird – it’s almost like having a second life. He’s evolving as I am, hopefully, in life.”

He’s always happy to hear from Marvel.

“It’s like Christmas morning when the call comes. Santa Claus still lives. We’ve been trying to find new things with [Bucky] and Marvel allowed that. It’s not like now, he’s a good guy and morally invincible. He always has to deal with what he’s done. That’s relatable. That’s all of us.”

Stan came a long way since leaving Romania and later Austria as a child. “I would always do impressions, so my mum thought: ‘He should try doing this.’ She took me to this open call for [Michael Haneke’s] ‘71 Fragments of a Chronology of Chance’ and I remember hating it.”

It wasn’t until coming across a “basement full of VHS tapes” in the U.S. and going to an acting camp “after years of wanting to be an astronaut” that things changed, leading to collaborations with such filmmakers as Ridley Scott, Darren Aronofsky or Soderbergh.

“When you get a little more successful, they respond. I’ve been very aggressive about it. I’m okay with saying: ‘I would really like to work with you.’ Sometimes it’s okay to let people know,” he laughed.

Stan recently starred in “A Different Man,” scoring an award at Berlinale – “An important step in my journey” – but as proven in Zurich, some fans never forgot his earlier roles either, including a lengthy stint on “Gossip Girl” as a troublemaking heartthrob.

“Some people never do. I still get it sometimes when I’m getting a coffee and someone whispers: ‘Carter Baizen.’ It’s like ‘Fight Club’ or something.”