As Miss Manners once said, it's not nice to fool people.

Even fiction has its rules. First, fiction should be identified as fiction; it shouldn't be passed off as truth. Secondly, fiction should have a moral sense. If a person tells a fictional story in which bad things happen, he should let you know somehow that he, the artist, knows that the bad things are bad. He shouldn't leave you with the impression that he's some kind of monster that lacks normal feelings of empathy, or a sense of justice.

See the film "Man on the Moon" in which Jim Carrey portrays Andy Kaufman. Andy was a talented comedian, but he sometimes got so carried away with bringing his characters to life—especially one obnoxious character that he called Tony Clifton—that he failed to let the audience in on the joke, and people were offended.

On the other hand, the mental confusion that you feel when you aren't quite sure whether someone is kidding—is often a "teachable moment" in which you ask yourself some profound questions like, "What is comedy, anyway? What is art?" Maybe Kaufman and the performer you saw, Emily, were trying to create moments like this—but I doubt it.