Like many world-class performers, Keith Urban has hilarious stories of his highly unpredictable life as a touring musician. He recently appeared on Conan O'Brien's late night TV show and revealed a few entertaining highlights of the past few months, including a body part he didn't think he'd ever autograph and what it was like to play with the Rolling Stones. 

The singer/guitarist thought he had heard it all...until a fan requested he sign her prosthetic leg. He explains that while playing a show, a fan yelled out, "Will you sign my leg?" Urban recounts that he thought, "Well, this will be a good moment. I'll bring her up onstage, I'll sign the leg." After the country star yelled out, "Sure!" to the enthusiastic fan, he was caught off-guard when she threw something onto the stage: her prosthetic leg. He laughs, "I sign it, and I'm thinking, 'What's the proper prosthetic leg returning etiquette?'" The leg was gingerly and safely crowd surfed back to its owner. It's not every day an artist can say they've signed someone's prosthesis.

Urban also received an entirely different surprise when Mick Jagger called him up to play with the Rolling Stones for the first show of their 50 & Counting Tour, and jokes that when the frontman called him and asked, he replied, "Let me think about it." He adds, "Before I knew it, I was at soundcheck at the arena and we did 'Respectable. 'It was amazing. It was a blast."

The 'American Idol' judge is looking forward to his 2013 Light the Fuse Tour, bringing along class-act openers Little Big Town and Dustin Lynch. With an anticipated album that is said to be different than anything Urban has ever done, and an exciting new single to be unveiled on Monday (May 13), he has lots of good things ahead. Hopefully, he'll have a lot more entertaining stories to share as well!

See More Keith Urban on 'Conan'