He's used to performing knockout shows, but even Van Morrison wasn't expecting Rocky to turn up for a gig.
The east Belfast blues legend is currently on tour in the US, and even smiled for a photo with Sylvester Stallone in Los Angeles.
Van - who was perhaps recalling his 1974 hit You Don't Pull No Punches, But You Don't Push the River - was playing at the Shrine Auditorium & Expo Hall in LA when Stallone popped backstage.
The Hollywood superstar was joined by Oscar-winning songwriter Paul Williams.
Van also delighted fans when he welcomed surprise guest Tom Jones to the stage for renditions of Sometimes We Cry and I'm Not Feelin' It Anymore.
Cindy Leath wrote on Facebook: "It was a treat to be sure. Such a surprise. Absolutely great night of stellar music."
Stallone recently labelled himself "an old dog learning new tricks" as he returned to play Rocky Balboa in the new film Creed.
The 69-year-old actor has now played the boxer seven times since the original movie, Rocky, was released in 1976.