A licensed doctor specializing in internal medicine, the 40-year-old Korean-American has embarked on a second career as a full-time comedic actor.
It was a nude Jeong (pronounced Jung) that Bradley Cooper, Zach Galifianakis and Ed Helms discovered in the trunk of their convertible in a Las Vegas impound lot in The Hangover. And it was his decision to bare all while playing Chinese gangster Mr. Chow.
"I think I have to be naked for this scene," he proposed to Hangover director Todd Phillips. "He said, 'You don't have to ask me twice.' Before I knew it, they were shoving waiver forms in my face for me to sign because they didn't want to give me time to change my mind."
But he had no fear because he had already shot All About Steve (in theaters Friday) with Cooper and The Goods: Live Hard, Sell Hard with Helms. "I felt very safe. ... I have so much trust in Bradley and Ed."
There was one person, however, whose blessing he sought before dropping trou: his wife and fellow doctor, Tran Ho. "I wouldn't have done anything in show business if not for her. She was the one who knew I was an actor and comedian at heart."
Jeong's parents also had his back. He says he inherited his sense of humor from his father, an economics professor.
"I took one of his statistics classes one summer," he says. "He worked the room and improvised like a stand-up comic."
He reports that his father "couldn't be giddier" about his first big TV role, playing ornery Spanish professor Señor Chang in NBC's Community (he shows up in the sitcom's second episode at 9:30 p.m. ET on Sept. 24). The way he describes it, "Chang had to plow through a lot of Alvarezes and Martinezes to get his job and has a chip on his shoulder about being an Asian Spanish instructor. You so much as look at him funny, you insult his honor."
Given roles like Mr. Chow and Señor Chang, Jeong is often asked about typecasting. It happens, he concedes — but not how you'd think: "My parts are all written for 50-year-old white men."
That was the case with his geeky, wannabe medieval King Argotron in 2008's Role Models and his parts in the upcoming Furry Vengeance and The Zookeeper.
The same goes for Angus McCormick, his rookie cable news producer in All About Steve. He's intimidated by his reporter, Hartman Hughes (Thomas Haden Church), and his cameraman, Steve Gunders (Cooper). "These guys have been through producers like Spinal Tap goes through drummers," he explains.
It wasn't hard for Jeong to put himself in Angus' place. He tapped into his own sense of being starstruck on set. "I couldn't believe I was working with these movie stars. I was wet behind my ears, both in my character and my career."
Jeong was more at home in his first movie, using his medical background to play the snarky obstetrician in Judd Apatow's Knocked Up, in which he says the cast improvised about 20% of their lines.
He counts Role Models as his most challenging role. "I had to do tons of research. I knew nothing about that world (LAIRE, or live action interactive role-playing explorers). I went to those events, watched and interviewed people."
But he did get some tips on how King Argotron should look. "Bradley suggested I should have a pathetic little mustache and goatee."
Because of filming schedules, Jeong's family (he and Tran have twin daughters, Alexa and Zooey, 2) spent Christmas Eve and Easter Sunday with the Cooper clan.
"I'm looking around the table at these gorgeous people," he says. "It's like they're Brad and Angelina and I'm their adopted kid. I'm Bradley Cooper's Maddox."