Does the first piece in a standard blokus game have to have a square on a corner cell?
According to the rues, "The first piece played by each player must cover a corner square." They show an example of an illegal first move, as a piece that "surrounds" the corner without touching it, like an X would. This does mean that the X cannot ever be the first piece.

http://www.mindware.com/Blobs/22021_inst_blokus.pdf