Dimensional Bleeding

Dimensional Bleeding is the phenomeno in which parallel dimensions bleed into one another. It is caused by the Slender Man tearing reality apart by moving around and cutting into other universes in such a manner that they droop into each other to fill in the cracks. When the different universes droop together, they mix and swap parts in a constant flow. These effects can most clearly be witnessed through the Internet, as different iterations of the same servers have swapped places and taken up the same physical space so often that the memory stored on them has been transferred and has allowed people to see into the lives of themselves or others in different universes.
Areas where Dimensional Bleeding occurs often enough will eventually become Rifts, places where multiple universes meet up and can be traveled between.
According to Mr. Collector, image of the Slender Man has also spread to these other universes and in some cases manifested into other corporeal and non-corporeal entities. He mentioned an entity known as the "Smiling Man" as well as the Creature as examples of this. He went on to say that each is a different entity with an identity borne from the Slender Man’s fingerprint left on the multiversal whole.