The Yes Men are prankster activists attempting to show the harm caused by global corporatism. They first became known for a fake GW Bush campaign site, for which the real GW famously said "There outta be limits to freedom."
Their movie has some truly hilarious pranks. The clips are on YouTube (of course!) but require some intros, as they are missing the long lead-ins which make them much funnier.
In the first, they pose as WTO representatives at a conference in Finland. After a presentation favorably comparing the use of third world sweatshops to slavery (among other outrageous statements), they whip out a demonstration, a futuristic business suit that allows managers to watch their workers by means of a giant phallic extension with a TV screen embedded in it, the Employee Visualization Appendage.
Amazingly, the stuffed shirts at the conference never catch on that they are being pranked. Here's the clip.
In another, they give a talk before an economics class to introduce a new plan to feed starving people in the Third World and at the same time make lots of money. After generously feeding the entire class with McDonald's, they show a video of the concept which is called "ReBurger." Let's just say that it would give new meaning to the phrase "ordering a number two." Here's the clip. Shocked and disgusted, the class ultimately does realize it is a joke.