"And now for something completely different." -John Cleese, Various Episodes
"It's not pining, it's bleeding demised! This parrot has ceased to be! THIS IS AN EX-PARROT!!!" -Angry Customer, Parrot Sketch
"It's a flesh wound!" -Black Knight, Holy Grail
"What's wrong with Biggus Dickus? My best friend from Rome is named Biggus Dickus!" -Pontius Pilate, The Life of Brian
Monty Python is a group six writers/comedians who made a show named Monty Python's Flying Circus that ran on BBC for a few years. They also made three movies: Holy Grail, The Life of Brian, and The Meaning of Life.
The show was made of a bunch of unrelated few-minute sketches that were quite funny. More famous sketches from the show and scenes from the movies are often (mis)quoted for laughs, although this is not as funny as actually watching the sketch. Obviously, it's been (mis)quoted or referenced many times in DYOS, most notably a parody of Holy Grail's "Camelot" Musical Sketch done by CivGeneral in DYOS 5.