Harpo Does Something Funny: When Jacques lists the countless meals he intends to serve at the dinner held by Harpagon, the actor is supposed to come up with his own list of exotic, expensive dishes. (If your edition of the play doesn't include the relevant footnote, then it looks as if Harpagon is freaking out over the very possibility of giving food to other people — though given how incredibly stingy he is, even that seems believable.)
Written-In Infirmity: Moliere, who suffered from a chronic cough, played Harpagon in the premiere; Harpagon is mentioned to be plagued by coughing as well.
