Cher

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

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. (PROSE: The Lonely Computer)

Ari Leventhal once saw a Cher concert. (PROSE: Doctor Who and the Adaptation of Death)

Behind the scenes
Carol Robinson frequently works with Cher as her wig maker and wig dresser.

Donna's line is in reference to Cher's song "".