http://en.wikipedia.org/wiki/Bleacher_Creatures
The Bleacher Creatures are a group of fans of the New York Yankees who are known for their strict allegiance to the team and their merciless attitude to opposing fans. The group's nickname was coined by New York Daily News columnist Filip "Flip" Bondy, who spent the 2004 season sitting with the Creatures for research on his book about the group, Bleeding Pinstripes: A Season with the Bleacher Creatures of Yankee Stadium, which was published in 2005.