M. C. Escher
Maurits C. Escher was an artist famous for creating confusing engravings. (AUDIO: The Forever Trap)
Graham Stevens had an array of Escher prints in his office. (PROSE: Cat's Cradle: Witch Mark)
The Seventh Doctor told Ace that she did for the English language what Escher did for spatial geometry. (PROSE: Lucifer Rising)
Laura Corbett said that the Land of Fiction was "very M. C. Escher". (AUDIO: The Crooked Man)
The Tenth Doctor compared the Edifice to "the steps that go up and up and join up". (AUDIO: The Forever Trap)
The Eleventh Doctor, while trapped in the Bank of England, jokingly remarked that it was designed by Escher. (GAME: The Eternity Clock)
Art student Jess Collins didn't like the work of Escher, but had to read Dimensions of Escher for art history. The Twelfth Doctor told her to never get stuck in an Escher painting because you will feel sick and finding a chemist is "a nightmare". (COMIC: Moving In)
Behind the scenes
The television story Castrovalva is named after the M. C. Escher's print Castrovalva. The titual city of Castrovalva featured confusing spatial geometry seen in M. C. Escher's work. The novelisation was dedicated to M. C. Escher.
Tom Connell's Castrovalva illustration for DWDVDF 47 Relativity
Doctor Who Annual 2011 references Another World
12DY2 10 Cover A references Hand with Reflecting Sphere