The Harry Potter star plays a dead guy in the wacky castaway film, which became a big hit at the Sundance Film Festival in Utah at the beginning of the year (16), and he admits one scene was stranger than other odd moments for himself and Dano.

"There's this very weird, incestuous triangle thing that has happened now with my and Paul's girlfriends," he attempts to explain during a recent appearance on The Jess Cagle Interview. "My girlfriend, Erin (Darke), played Paul's wife in Love & Mercy, and Paul's girlfriend, Zoe (Kazan), was with me in What If, and now Paul and I have also kissed on screen."

Radcliffe admits the film is a little out-there, and not for everyone, but he's thrilled with the end result, particularly one scene, in which Dano's character uses his gassy castaway-mate as a jet-ski.

"There is a scene where he rides me across the water like a jet ski propelled by gas," Radcliffe giggles. "When you read that, there is an element of, 'OK, yeah, that could be terrible...' But it could also be maybe the greatest thing I ever get to be a part of.

"(I thought), 'If I'm sitting here in two years watching someone else be a part of that scene, how will I feel?' That scene, the first time I saw it, there were tears of laughter and joy in my eyes."