Four Yorkshiremen
Absolute classic. I recently saw the original version on one of those top one hundred comedy history progs. I was surprised to find out that its not really Python at all. It was something like "That was the week that was" or "The Frost report".
Three of the four were John Cleese, Tim Brooke-Taylor and Marty Feldman, I can't remember the fourth but it may have been another Python.