The Eleventh Doctor assembled a quadricycle in 2013 from parts he found in Clara Oswald's garage, believing it to have been broken. When questioned, he realised that he had actually just invented it. (TV: The Bells of Saint John)
- In the real world, the Doctor did not, in fact, invent it. In fact, Henry Ford's first automobile in 1896 was called a 'quadricycle', due to its four-wheeled nature.
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