Incredibly huge moment for ‘Extremely Loud’s’ Thomas Horn

Thomas Horn, 14, was standing in the middle of a cocktail party populated with adults when director Brett Ratner walked over to the teenager to offer him a congratulatory pat on the shoulder.

Days before the late December release of “Extremely Loud & Incredibly Close” — in which Horn stars as Oskar Schell, a boy struggling to come to grips with the loss of his father, played by Tom Hanks, in the Sept. 11 attacks — he and other cast members were being feted in the lobby of a building that houses the Academy of Motion Picture Arts and Sciences’ Film Archive.

The event was filled with academy voters, studio executives and filmmakers including the famously brash Ratner, who recently resigned as producer of the upcoming Oscar telecast after using an anti-gay slur. Still, Thomas, looking grown up in a cable-knit sweater, dark jeans and shiny dress shoes, was doing his best to avoid any attention from high-powered strangers. He dashed off to the buffet table a few times, filling his plate with tomato salad and cookies. Otherwise, he mostly hung by his father’s side.

“As a parent and as a medical doctor, I have been used to — up to now — being the center of attention in our family,” Erich Horn, Thomas’ father and an eye surgeon, had said at a hotel an hour before heading to the party. “That’s changed. It’s been a different role for my wife and me to be here as purely a third or fourth fiddle. We’re guardians and accompanists, but this is his symphony.”

It’s been a swift adjustment for Thomas from a San Francisco ninth grader to Hollywood leading man, er, boy. It was only 12 months ago that he arrived home to a voice mail from his school secretary, alerting him that a casting agency was trying to track him down.

Turns out that “Extremely Loud” producer Scott Rudin had seen Thomas on an episode of teen “Jeopardy!” — during which he won $31,800 and a family trip to Alaska — and thought he might be a good fit for the role of Oskar, who is at the heart of director Stephen Daldry’s adaptation of Jonathan Safran Foer’s bestselling novel.

“We’d seen about 3,000 kids at that point, but there was a twinkle with Thomas — a strength, actually,” Daldry recalled. “We brought him to audition in New York and saw he was able to access his emotional life.”

The filmmaker soon offered Thomas the part, but there were some concerns — namely, that the boy would need to miss six months of school and get a tutor on set to partake in the production.

“There were some definite drawbacks, like my whole family had to rejigger the whole schedule and take off work,” said Thomas, holding a cup of tea over his mouth for the entirety of an interview at the tail end of his day in Beverly Hills. “But I was kind of captivated. They were offering me this kind of opportunity — why shouldn’t I take it? Nobody else gets this kind of thing, and I got it really easily. There must be some reason for this.”

Indeed, Thomas had virtually no acting experience — unless you count playing a grasshopper in a fifth grade production of “James and the Giant Peach” — and admits he’s never been especially interested in pop culture. During his turn on “Jeopardy!,” he nailed a $1,600 question about the location of La Giralda minaret, but skipped a $200 one asking for the name of the TV show on which popular tween actress Miranda Cosgrove stars.

He cites his favorite movie as the decidedly adult Clint Eastwood-directed apartheid drama “Invictus,” but has never seen his costar Sandra Bullock’s broader commercial hit “The Blind Side.”

Still, Thomas — who is fluent in Croatian and is currently learning Mandarin — took to the acting process quickly. His character displays symptoms of Asperger’s syndrome, so he spent time with his father and mother, a pediatric oncologist, learning more about the medical condition.

Daldry took his young star to tour the 9/11 construction site, and the pair met a number of individuals who had lost relatives in the tragedy. And he worked with a dialogue supervisor to figure out ways to get into character during Oskar’s most emotional moments.

“I would go into a place that was quiet and isolated and think about how my character would feel in the situation, considering who he was and what he had been through,” Thomas said matter-of-factly. “I would think about that even up to 30 minutes. And when I felt the character was in my body and I had left, I could walk onto set or into rehearsal.”

But his performance — which fills nearly every frame of the movie — has been met with a divisive reaction from critics. The New York Post, for one, blasted his turn, saying Thomas “gives arguably one of the most obnoxious child performances in Hollywood history.” Fortunately, the only piece of advice Daldry gave Thomas before his foray into Hollywood: Don’t read the reviews.

“There’s a lot of really nasty things out there,” the filmmaker said. “I was always expecting the vitriol, because the character is not a regular kid, in a lot of ways. He has all sorts of tics and phobias and is not an easily likable, Disney kid.”

In any case, Thomas said he isn’t sure if he’d like to be an actor when he gets older. He’s already considering going into computer science or law, though his agent — who also represents fellow kid actor and “True Grit” star Hailee Steinfeld — is still “screening opportunities” for him in Hollywood.

If he does end up in Tinseltown, though, he’d “like to be in the heartbreaking actor mold better than the partying celebrity,” he said earnestly.

In an email, Bullock wrote that she felt confident that Thomas “will do great things in life — whatever he decides to do” — a sentiment Daldry echoed.

“This will be a moment in his life, and that moment will pass and then he’ll be a regular school kid again,” said the director. “So is showbiz really the path he should go down? I think he should worry about it when he gets out of Yale.”

amy.kaufman@latimes.com