Other mistake: In the Y valley travel agents sketch Smoke Too Much states that he can't say the letter C. But he uses several Cs before Bounder suggests he uses the letter K, even saying "I can't say the letter B." He says that he'd never thought of the letter K before.
Other mistake: During the Toad Elevating Moment, John Cleese enters and says "Good evening," even though his character only says the beginnings of words (he should have said, "G- Ev-"). (00:06:05)
The Royal Philharmonic Orchestra Goes to the Bathroom - S1-E11
Other mistake: William Knickers' letter, complaining about the sketches, starts "I strongly object ..." but the voiceover says "I object strongly ..."
The Nude Man - S3-E9
Other mistake: During the "Olympic Hide and Seek Final," Terry Jones, as the Paraguayan, has a little difficulty with his Spanish numbers. Besides mispronouncing many of them, he says "quince," the Spanish number for fifteen, instead of "cinco," the Spanish number for five. He actually has to pause to remember the Spanish number for fourteen, "catorce".
How to Recognise Different Parts of the Body - S2-E9
Other mistake: The final 'How to Recognise' announcement is originally written as "Number thirty. The End." When the show was broadcast, it was "Number thirty one. The End", yet all the other numbering tallies with the script. So either Cleese miscounted on the night of recording or they inserted another one which was later cut.
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