He’s used to playing in front of thousands of screaming fans at stadiums around the world.
But Green Day frontman Billie Joe Armstrong decided to swap the big stage for a small one on Saturday night, when he walked into a London bar and joined a cover band for a rendition of his own hit song Basket Case.
The 50-year-old rocker stunned the patrons and the band members at Slim Jim’s Liquor Store in Angel, north London, by hopping on stage and grabbing the microphone.
The cover band, called Borderline Toxic, couldn’t believe their luck as they got to perform with their childhood idol.
They later shared a video of the impromptu collaboration on Instagram, writing: ‘The moment your band gets joined on stage by your childhood idol to sing their own song with you… in your favourite dive bar!! Billie Joe Armstrong… @greenday !! THANK YOU, YOU LEGEND! This was the first band to get me into rock when I was 11 years old and I’m honestly just so made up. BRB crying/screaming/spewing.’
Green Day also posted footage of the surprise performance on their YouTube channel, with the caption: ‘When you walk into a pub and the cover band starts playing your song.’
The video shows Armstrong singing along with the band and interacting with the crowd, who cheer and clap along.
The singer was wearing a black leather jacket, a white T-shirt and a black beanie hat.
He looked relaxed and happy as he belted out the lyrics to the 1994 classic from Green Day’s breakthrough album Dookie.
The song reached number one on the US Alternative Songs chart and number seven on the UK Singles Chart.
It is one of Green Day’s most popular and recognisable songs, and has been covered by many artists over the years.
But none of them could match the thrill of singing it with Armstrong himself.
One fan commented on the video: ‘This is so awesome. Imagine being in that pub and seeing Billie Joe just walk in and sing with the band. I would die.’
Another wrote: ‘This is why I love Green Day. They are so down to earth and humble. Billie Joe is a legend.’
A third said: ‘This is the coolest thing ever. I wish I was there. What a lucky band and audience.’
Armstrong was in London for a break after finishing his Hella Mega Tour with Green Day, which saw them play in front of 75,000 fans at the London Stadium last June.
The tour also featured fellow punk rock giants Blink-182, The Offspring and Good Charlotte.
Green Day are one of the most successful bands of all time, having sold over 75 million records worldwide.
They have won five Grammy Awards, including Best Rock Album for their 2004 masterpiece American Idiot.
They have also been inducted into the Rock and Roll Hall of Fame and have their own Broadway musical based on their songs.
But despite their fame and fortune, they still know how to rock out in a pub with their fans.