The best joke of the movie ?
I was just thinking back about the little jokes and one particular thing made me laugh, just by thinking about it:
There's this scene where Hulot carries some thing inside the house of those girl (as far as I can remember it correctly) and there are some suitcases in the door opening. Hulot can't see where he's going and thinks the stairs is just a few steps longer and falls flat through the door.
Really brilliant joke, since most of the time things happen unexpectedly and this one you can see coming for ages - the fun lies in the way the suitcases are perfectly aligned with the stairs.