The actors appeared on ITV's Daybreak on Friday for a chat about their new film Due Date with entertainment editor Kate Garraway but Gervais, who has no connection to the flick, soon arrived onset.
Comedian Ricky, 49, gave Kate a set of spoof questions and then tried to coach Robert, 45, and Zach, 41, how to give funny answers.
Gervais told the pair: 'As you know, I'm sort of in charge of comedy entertainment in Great Britain, so I've got to make sure everything goes to plan.'
The boys were all in fits of laughter as the interview descended into chaos.
Galifianakis said: 'Ricky emailed me, he knew I was going to be in town and said, 'Look, I really need to get on television again, this is my last ditch effort to get on top' - this is it, this is a sad attempt.'
Ricky added: 'I have made it on Daybreak! Go and see the film!'
Garraway then joked The Office star had had his time on Daybreak before she chucked him out of the interview.
Due Date, a film about a father-to-be [Downey Jr] who is forced to go on a road trip with an aspiring actor [Galifianakis] in order to make it to his child's birth on time, is out in cinemas now.