What film/series is the biggest source of quotes in your game?
Is it too cliched to say "Monty Python"?
I wouldn't say that all of our quotes derive from classic 1970s/80s British comedy, but a substantial number can be traced back to Monty Python, Hitch Hiker's Guide to the Galaxy, Tom Baker-era Doctor Who, and their ilk. These probably make up less than a quarter of the overall quotes, with a hefty proportion of Princess Bride, Star Wars, Aliens, classic 80s action movies, and a variety of other sources depending on what genre we're playing.
I actually think that regular silly accents play a stronger role in our games than quotes.