The Slender Man (also known as Slenderman) is a fictional supernatural character that originated as an Internet meme created by Something Awful forums user Eric Knudsen (a.k.a. “Victor Surge”) in 2009. Stories of the Slender Man commonly feature him stalking, abducting or traumatizing people, particularly children.  The Slender Man was a catalyst for the stabbing of a young girl in Wisconsin as her friends became obsessed with the character and thought luring their friends into the woods and killing her would appease him.

Slenderman Trial article

http://en.wikipedia.org/wiki/Slender_Man