Gervais suggested that Martin Freeman, who played Tim, was the easiest to crack.
"I saw [making them laugh] as my job," Gervais told Shortlist. "I remember Steve [Merchant] saying to me, 'It's not enough for you to just have your own show - you have to try to ruin it as well'.
"The record for a number of takes in one scene was 74. It was in the second scene, where Brent was giving Tim his assessment. I changed the way that I did it for every take and Martin just couldn't cope with it. He is such an 'actor', too - he loves his craft. He was probably sat there thinking, 'Who's this f**king fat buffoon who's never acted before? Why's he in charge?'"
However, Gervais explained that he found it very difficult to distract Mackenzie Crook, describing him as "f**king unbelievably professional".
"I had to revert to touching his knee under the table," he said. "And when I discovered that he had knees like a gosling, I couldn't believe my luck. He wouldn't exactly laugh - he'd just go, 'Hmm, can we stop? Ricky's touching my knee again, it's not right'."
Gervais also revealed that he does not regret ending The Office after two series.
"I miss it and I couldn't be prouder of it, but that third series... It might have been good. But it might not," he said.
Gervais previously suggested that the most recent season finale of the US Office had "jumped the shark" but later insisted that he had not "dissed" the show.