Roger Daltrey not only sang the CSI theme songs, he guest starred in the episode “Living Legend”…as five different characters.
As a Doctor Who fan, I was more stunned by John Barrowman (Captain Jack Harkness) showing up as one of Gandolfini’s aides. Barrowman was the lead on a TV show at the time, and the fact that he’d be in Zero Dark Thirty for just two or three lines of dialogue was jarring.