The actors worked together on the 2004 adaptation of Ian McEwan's acclaimed novel, which tells the story of a man who becomes obsessed with a fellow witness of a hot air balloon accident.
Ifans plays the film's creepy stalker and immersed himself in the role, but he eased the tense atmosphere by teasing Craig about their kissing scene.
He tells Britain's The Times, "To play him as some weird stalker wasn't good enough. I had to go somewhere that wasn't in Ian McEwan's novel. I had to be like an infatuated teenage girl, you know, with the big doe eyes and the playing with the hair, but very religious and very likable, someone who is overly attentive to the old ladies in church.
"But that whole film was so dark that I had to have a laugh with it. I spent the whole shoot winding up Dan Craig saying, 'Only four days to go now, Dan darling, before our snogging scene.' Even now, after two Bonds, Dan still maintains that the hardest stunt he's ever done was getting to grips with my mouth."