I missed the season finale of Law and Order SVU because I was watching the Frontline documentary: Storm Over Everest. But I quite enjoyed the previous episode called "Authority," in which Robin Williams plays a disgruntled sound engineer who expresses his years of stored guilt and rage by tricking gullable people into doing things that they wouldn't otherwise do. He does so under the guise of a fictional character named, Miilgram; the name is a reference to the famous "Milgram Experiment" (footage below) in which subjects were asked to administer what they believed to be real electric shocks of increasing voltage to paid volunteers. The shocks, of course, were not real; the subjects who were allegedly being shocked were confederates. The purpose of the experiment was to study the degree to which individuals would blindly follow authority.

Though it produced some very interesting results, today the expirement is widely considered to have been unethical. I, personally, am a strong beliver in informed consent and I don't necessarily think such an experiment is unethical so long as adequate informed consent is obtained (though, this very issue often presents a problem for psychological experiments, in general).
For fun, I included some actual footage from the Milgram experiemnt:

This footage was also included in the Enron documentary, The Smartest Guys in the Room - which I highly recommend.