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Graham Chapman (King Arthur) was the only member of the cast to wear real chain mail armor. It weighed about twenty-five pounds. The rest of the cast wore knitted wool, painted to look like metal. The weather conditions in Scotland and England being what they normally are, the actors spent most of the shooting days being very cold and wet. To make matters worse, the hotel where they were staying only had a limited number of baths and hot water. At the end of each location shooting, there was a dash to see who could get back to the hotel first. The Monty Python troupe all seem to agree that they did not enjoy much of the filming experience for this movie.
Funds earned by Pink Floyd's album "The Dark Side of the Moon" went towards funding this movie. The band were such fans of the show, they would halt recording sessions just to watch Monty Python's Flying Circus (1969).
The famous depiction of galloping horses by using coconut shells (a traditional radio-show sound effect) came about from the purely practical reason that the production simply could not afford real horses.
When this movie screened at the Cannes Film Festival, the audience laughed at the opening credits. However, the projector stopped and the audience just roared with laughter, thinking it was all part of this movie. It turned out there was a bomb scare, and firemen came in and made everyone in the cinema go outside.
During one of the first screenings of this movie in front of a live audience, co-writer and co-director Terry Jones noticed that when music was played during the jokes, there was a marked reduction of laughter from the audience. He went back and edited the music out whenever a punchline was delivered. At subsequent screenings, he noticed a dramatic increase in the audiences' positive reactions to the jokes. From that point on, whenever he directed, he remembered to stop the music for the funny parts.
Mark Zycon: Mark Zycon was a Monty Python's Flying Circus (1969) fan who showed up to the set one day. Terry Gilliam recalls him showing up in a taxi. They needed a double for Eric Idle at the time. Zycon was the right size, so they gave him the job. They learned shortly after Zycon would be willing to perform stunts, so he began doing things "no stunt man would do," says Gilliam. Zycon is seen briefly in the Camelot music sequence as the prisoner hanging on the wall.
Neil Innes: The head monk hitting himself in the head with a board. Co-director Terry Gilliam called Innes essentially the "seventh Python."