Among the various April Fool’s things on the web, the most subtle one I’ve found is by the people at James Madison University, who are advertising an April 1 event discussing the question of Is String Theory Scientific?
Update: Another April 1 effort, this one an essay on the multiverse by Robert Lawrence Kuhn. Kuhn claims that the majority of cosmologists disagree with George Ellis about the problems with the multiverse, and that Andrei Linde (with Steve Weinberg agreeing with him) represents the consensus viewpoint. Very funny.
Update: INTO THE MULTIVERSE: God’s Voice in String Theory is labeled March 31, but surely it too is an April 1 effort.