Cher

Cher was a musician from Earth who performed with Meatloaf in "Dead Ringer For Love".

Biography
At a time she was due in studio in twenty minutes, Cher was pulled out of time by Momus to help lead Planet 12 of the Ridion Alliance into a new age of enlightenment. Donna Noble was excited to recognise her in the crowd but couldn't get any reaction from the musician with a joke about "if she could turn back time." The Tenth Doctor, struggling to find an example to give Momus about how her absence would impact history, pointed out that there would never have been "Dead Ringer For Love". Donna noted that Meatloaf could have done it with someone else, which the Doctor conceded. (WC: The Lonely Computer)