AceShowbiz - Ken Jeong quit practicing medicine the day after he wrapped his part on 2007 movie "Knocked Up".

The actor developed his stand-up comedy routine while completing his medical residency and initially worked as a physician for several years at a Kaiser Permanente hospital in Los Angeles.

Ken's background in theatre led to TV appearances on shows such as "The Office" and "Entourage" in the mid-2000s, but it wasn't until he met director Judd Apatow on the set of "Knocked Up", in which he played Dr. Kuni, that pushed him to change careers.

"This is the first movie I did, I did while having my day job. I took a vacation week from my day job, I took four days out to play a fake doctor for four days," he said during an appearance on The Late Show with Stephen Colbert on Wednesday, June 27. "It was just heaven sent, working for Judd and I got to meet all my heroes in comedy. And to this day it still remains one of my favourite moments."

"The Hangover" star was thrilled to work alongside the likes of Seth Rogen, Katherine Heigl and Paul Rudd on the comedy. But it was being praised by Judd as his "discovery" that pushed him to pursue comedy full-time.

"I was very depressed going back to work. I couldn't go back, it was time to go pro. I didn't even want to see patients," the 48-year-old shared. "There were patients waiting for hours the next day, I didn't want to see them. I was a Debbie Downer the whole time and my nurse comes up to me and says, 'Dr. Jeong you have a patient in the examination room that wants to see you.' And I was like, 'Well nurse, you've got a doctor that doesn't give a f**k. I just did a movie, Carol. It was an Apatow. You don't get it, man.' I saw a couple more patients, then I quit."