Smile Dog

Smile Dog is the main antagonist of the Creepypasta story of the same name; "Smile Dog". He is a supernatural entity that takes the form of a demonic husky and forces people into spreading his image all over the internet, otherwise he will kill them, The origin of the image is unknown but is rumored to have been first posted on the /x/ (paranormal) board on the image board 4chan in 2008. According to the occult-related blog Aether Paranormal, the earliest known image tied to the story is the one shown above.

His appearance, he is believed to be a demonic creature resembling a grinning Siberian husky which appears in a photograph. When it is viewed by people, they will be plagued by nightmares. even these dreams will always feature of the Smile Dog. In it, the victim will usually ask what it wants. To which it replies with its famous line: "Spread the word", there is another other picture of him of course, he is similar to Jeff the Killer.

Spread
On January 15th, 2009, Urban Dictionary user smile.dog submitted an entry for "smile.jpg," describing it as a "haunted" image that it has: "a reputation for driving those who view it insane, making its victims view it in their mind's eye at every turn. While it has been discovered that these images in victims' minds are the result of epileptic seizures", there is a link to the image.

On August 27th 2009, a page for "Smile Dog" was created on the Creepypasta Wiki which only contains the image, However, someone added a full-story behind it, the artcle can be viewed here.

On December 4th, 2010, a user nu11 uploaded SCP-450 video which includes the image as a screamer part, It had over 140,000 views as of November 2014. The video is now private, but there are still copies of it.