Cultural references to the Doctor Who universe

Just as characters from other fictional universes have appeared in the Doctor Who Universe, elements of the Doctor Who Universe, have (for the most part, unofficially), appeared in other continuities.

Marvel
Marvel UK created a number of characters who appeared in various titles owned by the company, including Doctor Who Magazine (which was later re-named Doctor Who Monthly). The characters of the Special Executive (troubleshooters employed by the Time Lords, who had appeared in 4-D War and Black Sun Rising) appeared with Captain Britain in the "Jaspers' Warp" storyline written by the Special Executive's creator, Alan Moore.

The Doctor Who comics version of Merlin all appeared briefly in Captain Britain in a sequence demonstrating that Merlin had several alternate appearances and personalities that he could adopt as he saw fit. The Doctor has also appeared in cameos in several prose novels based in the Marvel Universe.

Marvel USA occasionally made oblique references to Doctor Who. These are largely the work of Chris Claremont, best known as the longest-running writer of the X-Men. Claremont's X-Men spin-off Excalibur featured the WHO, the Weird Happenings Organisation, led by Doctor Alistaire Stuart along with his sister, Brigadier Alysande Stuart. (They are obviously named after Alistair Gordon Lethbridge-Stewart.) The Marvel Universe has a thinly veiled version of the Doctor known as Professor Gamble who happens to have Dalek-like robot enemies known as the Incinerators (or Dredlox).

2000 AD
The 2000AD strip Caballistics, Inc. features Doctor Who references so often that they are practically part of the series' format. It however, it also depicted a character clearly intended to be the actor Tom Baker being murdered by Scottish nationalist demons. This would appear to undermine the frequent suggestion by Caballistics, Inc fans that the series is unofficially set in the Doctor Who universe.