Of his numerous jokes, I tend to enjoy most Haydn's plays with rhythm, especially in that he seems to be very conscious of how you'll hear the music and points out to you that he's pulled a sleight-of-hand on you. A prime example is the offbeat theme of the finale of Symphony 80. The listener is to be forgiven for hearing the initial phrases on the beat, since there's no context given, and then it's funny when we realize we've been had as the true beat emerges, but he carries it further: before the repeat of the opening there's a fermata, wiping the "pulse" slate clean as if shaking an Etch-a-Sketch, and one the repeat starts, damned if we don't again hear those three notes on the beat, even though now we know them to be offbeats. Then later in the movement he brings the theme back with the winds ticking the downbeats, and yet it's STILL hard to hear the theme as offbeat and the winds as on-beat. It's like a magician showing you how a trick was done while tricking you again.
A similar play occurs in the minuet of #77, where we get to the end of the antecedent phrase and it seems like all of a sudden the music has shifted to 4/4 without us noticing; we listen to hear what's going on in the consequent phrase and he doesn't do the trick there, it stays clearly in 3. But then he repeats and we get tripped up all over again. Then after hitting us with weird (almost Stravinskian) "random" accents, he returns to the opening version of the theme and we're ready to really pay attention and determine how he's fooling us, but this time, just before the trick (spoiler alert: it's changing the chord on the third beat of the second measure instead of the first beat of the third), he throws a seventh into the harmony to distract us and we are once again bewildered by the sense that somewhere in the phrase, somehow, we shifted into 4.
OK, OK, it's no bassoon fart, but still very amusing.