I always disliked the ending of Monty Python and the Holy Grail. Even though it was a comedy, I always hoped they would resolve the story, but instead the film ends with the entire cast being arrested. But I realized: This ending is, quite literally, a "cop out" ending. It is genius!
This troper saw it also clever for a different reason. It's a creative license interpretation to how the Legend of King Arthur ended; he goes to a climatic final battle, and ultimately killed in it. Here, he and every knight on the field were all arrested, ending the 'modern' parody of the legend.
It took my mother to point out the real punchline in the swamp castle joke: "They told me I was an idiot to build a castle in a swamp. But I built one!... and it sank into the swamp. I built another!... and it sank into the swamp. I built ANOTHER!... it burnt down, fell over and then sank into the swamp. But the FOURTH one!...THAT one stayed up!" Of course it would - it's got the last three for a foundation.
Momentarily laying aside the Rule of Funny, I thought it was curious that the Swamp Castle guards put up absolutely no fight against Lancelot's onslaught. It makes sense, however, if you figure that the King of Swamp Castle didn't hire guards that had combat training because Swamp Castle doesn't have any problems with invaders because no one in his right mind would want to take over a castle that's in the middle of a bloody swamp.
After the Big Reveal of Camelot, note the one person who notes that 'It's only a model' - Patsy played by Terry Gilliam. Of course he knows it's a model, he directed the film.
The irony being that it's not actually a model. It's a real castle!
When the two guards are arguing about the swallows and the coconuts, they mention the airspeed velocity of an unladen swallow. Maybe I was too young, or just not attentive enough the first few times I saw it, but that makes the later bridge scene even better, because Arthur did remember the conversation, but he took the pointless part, not the actual answer.
With the French taunting, one of the insults is "Your mother was a hamster, and your father smelt of elderberries!" Initially, it makes no sense, but, Genius Bonus sets in: hamsters are notable for being able to breed quickly, so essentially, King Arthur's mother was a sex maniac. Also, wine in medieval times was often made with elderberries, implying that his father was a drunkard.
The Frenchman was telling the truth when he said they already had the grail(and was laughing with his accomplices over the fact). The French didn't beat Arthur and Bedevere to the Castle Augh; the French castle was the Castle Augh, and the whole second half of the film consisted of the knights going in a huge circle to the back entrance.
"What is the capital of Assyria?" isn't just obscure, it's a trick question. Assyria had multiple capitals over its history, and since it was no longer a country by the time this is presumably set, any answer given would be wrong unless you treated it like the swallow question.