Plato on images that make one laugh

If seriousness appears as one central mark of philosophy (and Socrates is never depicted as laughing, except perhaps when exercising eirônia), Plato uses laughter in many key passages of his dialogues. In many cases, laughter (either experienced by the protagonists of the dialogue, or a laughter that is supposed to be experienced by us readers) is evoked by images. I will review some of them (mostly from Symposium), and try to figure out how they are supposed to work, and what philosophical gain we get from them