Stephen Hawking was a human scientist and theoretical physicist in the late 20th to early 21st century.
In 2004, Hawking attended the opening of the Tomorrow Windows at Tate Modern. (PROSE: The Tomorrow Windows)
When Dalek Thay encountered the Cybermen, Mickey Smith compared their traded to Stephen Hawking meeting the Speaking Clock. (TV: Doomsday)
Stephen Hawking died some time before 2050, where the famous scientist Alistair Gryffen used the phrase "Hawking's Ghost!" to express shock. (TV: The Last Oak Tree)
Behind the scenes
Hawking was interviewed as part of Doctor Who Live: The Next Doctor.
He was also portrayed by Benedict Cumberbatch in a 2004 BBC dramatisation of his time at Cambridge University.