Michael J. Fox made a surprise appearance during Coldplay’s headlining set at the Glastonbury Festival in England on Saturday. Using a wheelchair, the actor, who was diagnosed with Parkinson’s disease at 29 years old, joined the band with a guitar for the final two songs of their set, “Humankind” and “Fix You.” Frontman Chris Martin introduced Fox as “one who just totally rocks, with his Chuck Berry riff and the way he punched Biff,” and offered him a heartfelt tribute following their performance together. “The main reason we’re in a band is because of watching Back to the Future,” Martin said. “So thank you to our hero forever and one of the most amazing people on Earth, Mr. Michael J. Fox.” Fox and Coldplay previously joined forces onstage in 2016, when he performed Chuck Berry’s “Johnny B. Goode”—the song Marty McFly famously performs in Back to the Future’s school dance scene—at a show in New York. On Instagram the following day, Fox thanked the band and its team for a “f*cking mind blowing” time in Somerset.