Njorl's Saga - S3-E1
Audio problem: In the 'PC Pan-Am Gives Evidence' sequence (part of Series 3, Show 1), there is a loud, off-camera crash at 16'15", followed by hysterical audience laughter and a Palin visibly trying to stifle a laugh. This is because the heavily-bandaged 'Njorl', who had been replaced at that point by a dummy (enabling his head to be removed in the next scene), fell backwards off the podium, and had to be re-positioned by the crew. Filming presumably stopped, as a cutaway of Njorl appears in the middle of Pan-Am's address. The edit is also very audible, as Palin's speech suddenly plummets in volume.
Chosen answer: That would be Terry Gilliam, who played a lot of non-speaking roles in the series, and some speaking ones like Cardinal Fang in 'The Spanish Inquisition.' He did all the animation as well, but I'm sure you knew that.
rabid anarchist