Incident at Loch Ness
Penn, who wrote and directed this film, gamely sends up the Hollywood establishment by playing himself as a total sell out now that he has achieved the "power" of the producer. He does all the things that he himself, as a screenwriter, would hate -- hiring a model to pretend to be a sonar operator; planning a fake Nessie for the cameras, etc. All of this is done behind Herzog's back. While Herzog is trying to make a documentary about why people choose to believe in myths like the Loch Ness Monster, Penn is trying to "sex it up" and turn the film into a blockbuster.
Of course, the inevitable happens -- they encounter the real thing. But even though this is inevitable and we expect it, the film really creates an entertaining experience along the way. The growing tension between Penn and Herzog, especially as Herzog discovers Penn's lies, is palpable, and Herzog is a pretty naturalistic actor. One throwaway comment by Penn, after Herzog has called him out, was priceless. I can't recall the precise wording, but it was something to the effect of: "At least I didn't drag a boat over an island," to which Herzog spins and says, "What did you say?"
This is, of course, a reference to Herzog's Fitzcarraldo as well as his reputation as a dictatorial, crazy filmmaker.
It's a smart film that works overtime to maintain verisimilitude and convince you that it's real. In fact, the only thing that prevents the viewer from really buying into it is that, had these events really occurred on the set of a film by such a noted director, the whole world would know about it (or at least the film buffs likely to watch a film by or about Herzog).
If you have the opportunity, I recommend you check it out.