Monty Python Live at the Hollywood Bowl - Terry Jones's Wig
In the scene leading up to the Lumberjack Song (Dead Bishop) when the Church Police enter because Graham found the dead bishop, Terry Jones (the wife) flips his head and his wig falls off. I know that this is Python, but I am postive this was not done on purpose.
This was definately not done on purpose as you can tell by the reactions (trying to hold in laughter for the most part) of everyone else on stage. Since it is pretty impossible to cover a mistake like this, one of them (Graham i believe) moves sideways in a VERY noticable way to cover up Terry putting the wig back on, and Terry actually puts it back on backwards (the bun is now in the front of his head.) VERY amusing to watch!