How do you upstage Brad Pitt...offstage?
Easy, just as Bradley Cooper.
The actor masterfully photobombed Pitt as he took a selfie with a fan, musician Chris Simmons, at the 2017 Glastonbury Festival in England Friday.
"When you get your photo with Brad Pitt photobombed by Bradley Cooper!" Simmons wrote on Instagram, alongside the pic.
British rock band Royal Blood also posted on Instagram a photo with Pitt, joking that he was a fan who had won a meet-and-greet contest.
Cooper also surprised fans at Glastonbury when he crashed Kris Kristofferson's set to film a scene for his movie A Star Is Born, his directorial debut, starring Lady Gaga. He plays a country singer in the film.
As Kristofferson's set concluded, a brief glimpse of Pitt backstage flashed up on screen, The Guardian reported.
Other celebs who appeared at the festival this week included Kit Harington and girlfriend and former Game of Thrones co-star Rose Leslie, Suicide Squad star Margot Robbie, David Beckham and son Brooklyn Beckham and Johnny Depp, who stirred controversy by making a joke onstage about assassinating President Donald Trump, for which he later apologized.
Other performers at the festival included Radiohead, who performed their biggest hit "Creep" as well as songs like "Paranoid Android" and "Karma Police," Katy Perry, Lorde and the Foo Fighters.