Zach Galifianakis called Bradley Cooper to apologise for calling him a "hot idiot"

Fortunately, his friend wasn't offended.

He said: "There's something in the trailer and he's not even in the movie, but I refer to him as a 'hot idiot'.

"I called him when I saw the trailer...I was like, 'I called you a 'hot idiot.'

"He just laughed. He doesn't care. He's good-natured that way.

"I don't want to hurt people, but I do want to make them feel weird. There's a fine line there."

Zach had been wanting to expand 'Between Two Ferns' for some time but initially thought it would be "risky" to do something longform with the online skit.

He told Variety: "A few years ago we were going to try to make it a TV show, a behind-the-scenes of 'Between Two Ferns,' but a friend of mine told me no one would be interested in that and at the time I agreed with him.

"I like doing these but to take a sketch and blow it up into an hour and a half narrative, it's risky."

The movie includes cameos from the likes of Jon Hamm, Matthew McConaughey, Tessa Thompson, Keanu Reeves, Tiffany Haddish, Chrissy Teigen and Benedict Cumberbatch but none of the celebrity guests had been booked before they started shooting.

Zach recalled: "We just started filming things. Once we got some guests, people switched their schedules, storylines changed because we were writing on the fly and that's a tricky thing to do...In the end, it was so much fun to do."

Director Scott Aukerman added: "We just wanted to have fun every day and improvise and who knew that was going to happen and that's what we did."