Enforced Method Acting: At the end of the infamous Mr. Creosote scene, an extra (in the bottom right-hand corner) can be seen actually vomiting from sheer revulsion. He wasn't the only one - the sketch was apparently filmed in a warehouse with no air conditioning and the fake vomit smelled TERRIBLE (it was dairy-based and after a few days of shooting it was going off).
Hollywood Accounting: Eric Idle, on his Exploits Monty Python concert tour at the Turn of the Millennium, noted that this movie was the only Python film made with major studio backing (Universal Pictures)...and thus the only one that apparently didn't turn a profit. So in this tour's version of "The Crimson Permanent Assurance", there's an additional verse about studio accountants.
Nobody Ever Complained Before/You Never Asked: The reason why the Crimson Permanent Assurance short film went over budget and originally ran about half an hour (the movie trimmed it down to sixteen minutes). Terry Gilliam explained that nobody told him to stop.
One of the dinner guests who get taken away by Death is Simon Jones. This is especially uncanny given that the afterlife appears to be some kind of restaurant. And humourously, he plays the husband of Terry Jones.
One of the elderly accountants in the "Crimson Permanent Assurance" is none other than the Supreme Dalek himself, under his human alias John Scott Martin.
Throw It In: The line, "Hey, I didn't eat the mousse!" was improvised on the spot.
What Could Have Been: The second verse of "The Galaxy Song" was meant to be an animated sequence along with the instrumental part, but Terry Gilliam opted out of animating it in favor of shooting more of "The Crimson Permanent Assurance".
According to the DVD audio commentary, this segment was a remnant of a previous draft of the film, where all of Monty Python were going to be convicted at the beginning of the film for trying to use it as a tax dodge, and each be sentenced to death in a manner of their choosing.