Bradley Cooper makes surprise appearance on Glastonbury Festival stage

Actor Bradley Cooper surprised fans by taking the stage at the Glastonbury Festival Friday, since he wasn't exactly part of the lineup.

The Hangover star was shooting a scene for the upcoming film A Star Is Born, which he is also directing. Lady Gaga, Sam Elliott and Dave Chapelle are also part of the cast.

The film is a remake of a story about a woman who begins her ascent in show business and becomes involved with another musician who soon finds his career on the decline. The 1954 musical featured Judy Garland and the 1976 drama starred Barbra Streisand and Kris Kristofferson.

In fact, Kristofferson, who co-starred with Cooper in the 2009 romcom He's Just Not That Into You, was next to perform on stage after the shoot wrapped. Cooper introduced him and thanked the crowd.

The American Sniper actor also filmed scenes at the Coachella music festival in Indio, Calif. in April alongside Lady Gaga. In that instance, festival-goers were told about it in advance.

Cooper was caught on camera again at Glastonbury when he photo-bombed a picture by musician Chris Simmons, who was snapping a selfie with Brad Pitt. The Moneyball actor was also attending the music fest.

A Star Is Born is expected to hit theatres in September of 2018.