The first actual Yes Men project had its genesis in November 1999 when Andy, inspired by the anti-globalization protest about to shut down the WTO, made a satire of the WTO’s website (full live version here)… and the real WTO strangely issued an enraged press release in response.
The Yes Men, of course, promptly sent the WTO's release to thousands of journalists, and the resulting flurry of web press confused the era's primitive search engines. Searches for "WTO" would then sometimes end up at the Yes Men's transparently satirical site, resulting in a great deal of email from important visitors—including, eventually, a conference organizer who invited the WTO director, Mike Moore, to speak.
That's how one "Dr. Andreas Bichlbauer" found himself lecturing a roomful of lawyers in Salzburg, Austria about the finer points of the WTO’s free-trade ideology: how minimizing violence through tariffs was unacceptable; how siestas and such should be outlawed as barriers to corporate profits; and how democracy would be dramatically improved by letting corporations buy votes directly from citizens.
No one objected. Nor could conference attendees recall anything offensive about his speech—not even when they were informed that "Bichlbauer" had died from a pie to the face. See the whole presentation here, read the convoluted correspondence chain here (or as summarized in the New York Times here), and watch the whole video here.