This is a light-hearted episode that was supposed to make the audience laugh; but it is also one of the most hated episodes among the die-hard fans. Among the bones they have to pick are: it is lame that exactly one character is not affected; there is no real menace; it does not add to any of the general story lines; and the usual been-there-done-that nonsense.
All these arguments are obviously pointless – you cannot criticise an episode for not achieving something it never aimed for. This episode was an attempt at comedy, so the only valid question is, was it funny?
The answer is difficult. Yes, it was extremely funny in many scenes, starting with Elizabeth jumping in her chair when Lucius takes her hands, or all the characters acting out of their usual roles around Lucius. But it does become clear that the cast is unfamiliar with comedy, and so some of the scenes do not quite work out.
Also, I would not have chosen Richard Kind for the role of Lucius. I like him, but I never thought of him as one of the great comedians of our time. He does fit the role, though.
All in all, the premise is good, the plot is good, but the actors can't pull the weight (which might not be their fault; who directed this?) But if you like the cast in general, then this is a fun episode to watch.