The movie star thrilled attendees towards the end of the Music On a Mission event, benefiting the Mending Kids medical organisation, by quietly walking onstage at the Lucky Strike Live Hollywood venue to join the house band for a performance of his Hollywood Vampires bandmate Alice Cooper's School's Out hit.

Depp then remained onstage with his white electric guitar to play with KISS star Simmons as he came out to close the show with a rendition of his group's Rock and Roll All Nite.

The actor didn't say a word to the audience throughout the set, and simply waved as he left the stage at the end of the night.

The Music On a Mission concert, which raised funds to provide free corrective surgery for children around the world, also featured a surprise appearance by reunited rockers Extreme, who belted out their 1991 classic More Than Words.

Depp's surprise collaboration with Simmons took place a day after he stunned fans at the Disney D23 Expo in California on Saturday (15Aug15), when he dressed up as his famous Pirates of the Caribbean character Captain Jack Sparrow to tease the release of the franchise's latest sequel, Dead Men Tell No Tales.