The first time I saw it, I was alone in an almost empty cinema on a Saturday afternoon. My immediate response was “This isn’t funny, it’s just dumb!” (Obviously I had had almost no exposure to MP before this.) The only part where I laughed was when Lancelot kicked Princess Lucky in the chest.
I went to see it again with some friends on a Friday night a couple of weeks later, and the cinema was packed. That time, I laughed my ass off!