A bit of toilet humor, a bit of blunder, caricatural characters and quite a lot of predictability seem to make the ingredients of a French cult movie. At least this is the conclusion after watching this one in particular.
I recommend it nonetheless because there are some funny scenes in it - and I'm not counting in the one where a foreigner with an Eastern-European accent, which is somehow considered funny, offers his neighbors some shit-looking (literally!) Christmas cookies then candidly explains how he made them: by carefully rolling them under his armpits... This scene cracks the French audience up every time! The movie can make for a weariless conversation subject, at times when you will be dismissed from all discussions about food on the grounds that you're an ignorant foreigner. You will soon find that you're also an ignorant in the movie department, but that's another story.
In "Santa Claus is a Stinker" we are far from the traditional happy, placid Christmas spirit: its characters are neurotic, unadapted and plain awkward but this is the type of characters tremendously appreciated in here, as they're considered complicated and deep. Complexity is a great attribute to be had in France (ask the French public institutions!) because it represents the opposite of simplistic (as opposed to simple) and in the end nobody wants to be considered a simpleton, right?
Any French will be able to recall full dialogues from "Le père Noël est une ordure" but it's even better when you watch two of them talking about it: they will launch each other scattered lines, will complete each other's sentences then they'll laugh uncontrollably, incapable of explaining why they do so to the outsiders. Step back and wonder because it's quite a spectacle, not to be missed!
And now, let the protests of an invisible French crowd start, reproaching me the complete and hopeless misunderstanding of French humor. Amin!