Peter Cushing (in-universe)

Peter Cushing was an Earth actor in the 20th and 21st centuries. Cushing was friends with the Doctor, who took him on as an occasional companion, allowing Cushing to appear in films made long after his historical death. Among the roles he played was a fictionalised version of the Doctor.

Association with the Doctor
At some point, Peter Cushing befriended the Doctor, who allowed him to appear in movies made after his death. (PROSE: The Day of the Doctor) In 2065, eighteen months after the Thal-Dalek battle on Skaro, Cushing starred in Dr. Who and the Daleks, a Technicolor film based on these events, as "Dr. Who". (PROSE: Peaceful Thals Ambushed!) The Doctor loved the film, and lent him a waistcoat for a second one, Daleks: Invasion Earth. (PROSE: The Day of the Doctor)

20th century film career
By 1969, Cushing had starred in a film once watched by William Bishop, whose plot concerned a cursed stone. (PROSE: Mind of Stone) Cushing attended Iris Wildthyme's party in Hobbe's End in 1972. (PROSE: From Wildthyme with Love)

After attending the Star Wars premiere at Mann's Chinese Theatre with Frobisher in May 1977, the Sixth Doctor remarked that Tarkin looked familiar and that he seemed to remember meeting his granddaughter once. (PROSE: Mission: Impractical) Clara Oswald later knew of Cushing as "the guy from Star Wars". (PROSE: The Day of the Doctor)

A new "Dr. Who" movie
After the 2013 negotiations between the Zygons and UNIT in the Black Archive (TV: The Day of the Doctor) entered their ninth hour, the Tenth and Eleventh Doctors decided to blow off some steam by watching a VHS tape of Daleks: Invasion Earth. They greatly enjoyed the experience and subsequently pitched a third "Dr. Who" movie to Cushing over the TARDIS telephone. (PROSE: The Day of the Doctor)

Cushing subsequently starred in the 1980 science fiction film Prey for a Miracle, which was inspired by the UFO / gods scare caused by the Latter-Day Pantheon in New York City in March and April 1965. He played the lead role of "the mysterious government adviser, Doctor Who", a character loosely based on the First Doctor. However, a film critic for the magazine Film in Focus noted upon the film's release in November 1980 that Cushing's "endearingly eccentric professor [was] as fictional as the rest of Prey for a Miracle" as what little was known about the real life "Doctor" suggested that he was "a shadowy, manipulative figure." (PROSE: Salvation)

Later life
UNIT were aware of Cushing having died at some point prior to 2013, hence their surprise when he kept appearing in movies postdating his death. (PROSE: The Day of the Doctor)

Legacy
Upon meeting a dashing old gentleman during an adventure underground, Iris Wildthyme reflected that he had "an air of Peter Cushing about him" in a letter to Panda. (PROSE: From Wildthyme with Love)

Lawrence Burton wondered to himself if the Enemy might be "those outer space robot people" that appeared in "at least two films with Peter Cushing". However, he dismissed the possibility as implausible. (PROSE: We Are the Enemy)

Behind the scenes

 * The incarnation of the Doctor who originally befriended Cushing is not firmly identified, although as the Third Doctor in A Visit to the Cinema seems unaware of the circumstances of the filming of Dr. Who and the Daleks and refers to Cushing as "Van Helsing", it is likely that it was at a later point than this point in the Third Doctor's life that the two developed a closer association.
 * Film Star Wins Oscar—Misses Premiere! parodies Peter Cushing and Dr. Who and the Daleks as Seamus Vampire and Doctor Da and the Humanies.

Information from invalid sources
Trying to play The Universe Marathon, Peter Cushing lost his counter. (NOTVALID: The Universe Marathon) On Gallifrey, Roberta Tovey placed a classified ad looking for "her Grandfather, who answer[ed] to the name Van Helsing". (NOTVALID: TARDIS Stolen!)