Puss in Boots

Puss in Boots was a fairy tale. While connected to a P-series Genesis III, the Fourth Doctor recalled the story. Unable to imagine a talking cat, the computer was disabled. (PROSE: Inter-Galactic Cat)

Behind the scenes
William Hartnell's next appearance after leaving the role of the First Doctor was in a pantomime production of Puss in Boots, not three months later, which advertised a "Super Win-a-Dalek Competition".