It was originally going to be a radio show, but Talkback persuaded John Lloyd to take it to television as there wasn't any money in radio.
I WANT DONKEY CHEESE!
Jo Brand tells an anecdote about Arthur Conan Doyle, that he sent some friends a letter saying "All is discovered, flee immediately", and one of his friends then disappeared. This is something Mark Twain did, not Arthur Conan Doyle.
The researchers who provide the questions and information for Stephen Fry are credited as "QI Elves" which is how they are referred to on the show. Occasionally they are also given other interesting titles like "Curator of Jack and Jill" These can be seen in the "Cast And Crew".
Occasionally the arrangement of the opening/end credits music would be modified slightly to match the theme of that particular show. So, for instance, when the given topic was something like "All things french", an accordion would be heard prominently in the mix. But perhaps the most obvious case of modification would be in the "Holiday Special", where in addition to jingle-bells being added, the first two lines from the song by that same name were cleverly integrated into the music - thus adding three more notes to the second line of the main melody.