In 1975, a Manchester team including future Times columnist David Aaronovitchnote whose father, Sam Aaronovitch, was a senior member of the Communist Party of Great Britain protested at the rule allowing multiple Oxbridge colleges to enter (each university can field up to five teams per year) by answering every question with the name of a revolutionary figure ("Trotsky", "Karl Marx", "Lenin", or "Che Guevara") in the hope of rendering the show unbroadcastable. The episode aired anyway, and went down in history as one of the competition's more memorable moments. Manchester were, however, effectively banned from University Challenge for at least a decade.
There was also the incident where a New Hall, Cambridge contestant protested that the question should have been worded "what is it for?", not "what is it?" as the literal answer to the latter is "an oak leaf", whereas the question writer's intended answer was what the oak leaf sign signified.
Questioning of the given answer has occurred at least a couple more times besides.