I apologize if this is the wrong place to post this, but I'm really confused about this one line. I've been watching Cheers to improve my English because a colleague of mine recommended it to me and said that it would be a good way to improve my English. I've been watching it, and some jokes I'm able to understand, but some I completely miss. One such joke is in season 5 episode 2, and is as follows:
Diane: Sam... let's call an end to this nonsense right now. I don't care how rough you were on her; that is not Vicki. See, I know Vicki left. I've known all along.
Sam: And you let me go through this whole stupid act?
Diane: Well, I wanted to see how far you'd go-- ordering two sets of meals, leaving empty bottles of Vitamin E outside your door...
After Diane says this line, the audience laughed. I, however, didn't understand the joke at all. Is this a euphemism of some sort in English? Or is the joke funny for another reason? There are other euphemisms that I've been able to look up and understand, but I can't find any information about this one. The full transcript of the episode can be found here.