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".
The on-screen credits for each episode of Series 16 (the P series) include a credit for a Puzzle Wrangler called Pandora. The "surname" of this "person" changes with each episode. These are clues to a puzzle, with a mystery prize to be revealed for one lucky winner at the end according to the programme makers.