Alicia Vikander said Matt Damon left her constantly "on edge" on the set of Jason Bourne - because she was waiting for him to prank her.
The Swedish actress finally looked relaxed as she walked the red carpet for the film's European premiere in London's Leicester Square, alongside Matt, who reprises the role of former CIA assassin Bourne for the fourth time, and Julia Stiles, who returns as Nicky Parsons.
Alicia plays Heather Lee, the head of cyber intelligence at the CIA, who is caught up in Bourne's quest to find answers to his past in a "post-Snowden world", and sees him taking the car chases and fist-fights to Las Vegas, London, Athens and Berlin.
Despite being the "new girl", Alicia said the cast "made it feel like you were entering a family" - although with a little extra paranoia thrown in for good measure.
She said: "They love a joke and prank on set. They never got me, I was on edge most the time, but I think Matt's going to come for me at some point."
Matt, who is renowned for playing pranks on friends George Clooney and Ben Affleck, said he "took it easy on Alicia" because they were so lucky to have secured her.
"The truth is we felt so grateful she did the movie. Every single person in the world is trying to get Alicia Vikander in their movie right now, she's the hottest thing in Hollywood, it was huge for us," he said.
Also attending the premiere were British actor Riz Ahmed, who stars as tech wunderkind Aaron Kalloor, and director Paul Greengrass, whose presence on the film was the only thing that convinced Matt to sign on for a sequel nine years after he last starred in the franchise's Bourne Ultimatum.
Jason Bourne is released in cinemas on July 27.