Harry Houdini

Harry Houdini was a famous magician on Earth. He met the Doctor and taught him how to contract the muscles, which helped the Doctor escape from the Eight Legs on Metebelis III. (DW: Planet of the Spiders)

Between 1917 and 1920, Houdini, along with Sir Arthur Conan Doyle, publicly announced the existence of fairies following the release of the Cottingley fairy photos. Gwen Cooper believed this was all an act of self-publicity. (TW: Small Worlds)

Whilst handcuffed, Donna questioned the Tenth Doctor as to whether he had ever met Houdini. (DW: Planet of the Ood)

While tied up on Nerva Beacon, the Fourth Doctor recalled an encounter with Houdini. (DW: Revenge of the Cybermen)

In Area 51, when the Doctor, Cassie, and Jimmy were trapped on a 'table', the Doctor managed to break away from the hand cuffs, and turn off the Amnesia gas. This was a trick taught to him by Houdini. (DW: Dreamland)

The Eleventh Doctor, in 16th century Venice, entered an underground cellar, and met five female "Vampires". When he saw that they could be seen in the mirror, he compared it to a trick by Houdini. (DW: The Vampires of Venice)

Behind the scenes
Houdini actually never investigated the Cottingly photos, despite some correspondence from Conan Doyle, that suggested he visit. Houdini was shown to be involved in the events in the 1997 film FairyTale: A True Story.