Stephen Fry and Alan Davies were originally cast as the leaders of the "clever" team and the "stupid" team, respectively. Michael Palin was asked to be the host, but he didn't feel he was right for the role. After Fry and Davies settled into their roles, the idea of having two teams was discarded.
Stephen Fry revealed that there is one panelist who insists on seeing the questions in advance so that he or she can prepare their answers. Fry refused to name the person but did confirm that it was neither Alan Davies nor Rob Brydon.
Alan Davies has appeared in every episode of QI except one. In the 'D' series in 2006, it was written into his contract that he would be allowed to go to the football if Arsenal got to the Champions League Final. They did, and he went. Arsenal lost 2-1 to Barcelona.
The BBC and Talkback issued an apology in January 2011 after the Japanese Embassy made a complaint over a question and answer about Tsutomu Yamaguchi, the only man officially recognized as a survivor of both the Hiroshima and Nagasaki A-bomb explosions, who was described on the show as "either the unluckiest or the luckiest [man in the world], depending on which way you look at it".
Blue whales are a recurring joke on the show. Occasionally, a question will be phrased in such a way as to suggest blue whale as the answer, only for Alan Davies to guess blue whale and get it wrong to uproarious laughter from the host and the audience. Inversely, some questions will be phrased in such a way to truly flummox Alan Davies, only for him to be mockingly chastised for not guessing blue whale. As such, Alan Davies will occasionally guess blue whale even when it has nothing to do with the question or theme.