Smile Dog
From Screamer Wiki
Smile Dog is a classic Creepypasta character. He has creepy eyes and has yellow creepy teeth. He is similar to Jeff the Killer.
About Smile Dog's Story
Smile Dog's story consists of a classic horror set-up – an amateur writer visits the house of a lady who supposedly has a story for which he can borrow from. Rather than speak, however, the lady has locked herself up in her room, crying and ranting about nightmares and visions and various other problems. All of these center around a floppy disk she had been given that contain the image smile.jpg – which is smile.dog. Other cases of this have cropped up...
Viewing this image incites insanity, and no copy of the exact image exists on the web though likenesses of it do. The true image of smile.jpg is recognized due to the effect it has on the viewer – that is, they wind up dead. Attaching the file – that is, spreading the word, is the only way to save oneself from the smile.dog that appears in one's dreams demanding to spread the word. Some say that the original legend began with an image of the devil.