The film is in theaters June 3

By Jessica Fecteau
Updated May 25, 2016 10:00 PM
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Credit: Stephen Lovekin/Variety/REX/Shutterstock

The friendly chemistry between Emilia Clarke and Sam Claflin in their new romantic drama Me Before You wasn’t just for the cameras.

Claflin told PEOPLE at the film’s premiere in New York City on Monday they were pulling extreme pranks on each other behind the scenes.

One prank that stood out to the 29-year-old actor involved the Game of Thrones star, 29, putting fish in his socks.

“I was a little angry!” Claflin told PEOPLE, laughing. “No, I laughed but I made her think I was deeply offended. I think in fact that was the biggest prank – me pretending I was really upset.”

“She got really, really upset, like really felt bad, really felt guilty, so I think I win!”

But no good prank goes without revenge.

“I stole all of her furniture from her dressing room and shoved it in mine, which I thought was pretty special,” Claflin said smiling.

Since the pranks were taking place off camera, the film’s director Thea Sharrock says she didn’t find out about them until after they wrapped.

“Because I was like the mother figure they never told me until afterward,” she said. “I heard the things they had been doing to each other and I was like, ‘Oh my god ‘ ”

But she assures the pranks were simply a part of their playful chemistry and “no animals and no children were harmed in the making of this movie.”

“There were a lot of tears, but most of all there was a huge amount of love and a huge amount of laughter and I hope that comes across in the movie,” Sharrock said.