Almost every community has its own urban legend. Where I grew up in North West England the local 'lore', and a surprisingly common one too, was that the statues in the local graveyard were alleged to be able to move during the night. Of course, everyone knew someone who had seen it happen but alas nobody had seen it for themselves. Sometimes these tall tales inspire the dark imaginings of writers and authors, and sometimes the legend itself becomes so popular it becomes a phenomenon.
One such example is the Slender Man. Created by Eric Knudsen for a 'Meme' competition on the Something Awful forums (Eric's original memes pictured below). This supernatural creature was depicted as a tall, gangly, faceless man wearing a black suit and tie. Some other depictions also show the creature to have long tentacles sprouting from its back which it uses to walk, suspending its body off the ground.
The Slender Man is typically featured in manipulated photographs and videos stalking those shown in the foreground, typically children. Commonly the Slender Man is shown to be out of focus, transparent or otherwise 'apart' from the rest of the imagery. While this is probably due to the difficulty of believably superimposing an artificial image onto live action photography, the lore surrounding the character explains this away, citing the creatures otherworldly nature as the cause. The Slender Man is also claimed to be able to communicate telepathically and teleport short distances.
The Slender Man has influenced popular culture, being cited as an inspiration for the recent Doctor Who villains known as the Silence and the Minecraft mob the Enderman. Sadly the Slender Man has also reportedly been the inspiration behind less savory news headlines such as the stabbing of a teenage girl in Wisconsin in 2014, and a mass suicide attempt in South Dakota in 2015, among others.
Having amassed such notoriety it really comes as no surprise that Screen Gems is reportedly developing a movie based on the folklore urban legend. Based on a script by David Birke (13 Sins) the movie is slated to enter production this fall with a possible 2017 release date. The director and cast are unknown at this point as is whether or not the Slender Man will be depicted with or without his 'Lovecraftian' tentacles.