Billie Piper (in-universe)

According to radio newscaster Rosemary Stark, Billie was a British singer and actress whose birthday fell on 22 September. Tegan Jovanka turned off the radio before she heard Billie's surname. (AUDIO: The Gathering)

Behind the scenes
Billie Piper played companion Rose Tyler, and was in fact born on 22 September 1982.