Creepypasta/WMG

A malevolent, inter-dimensional being is driving our favorite cartoons insane.

This being is responsible for many "lost episode" Creepypastas; let's start with Squidward's Suicide. The story consists of Squidward comitting suicide after a horrible day. Note Squidward's red eyes on the page image. Next, we have Suicide Mouse, a surreal clip consisting of Mickey Mouse walking down a road (Worse than it sounds). Note the theme of suicide occuring. This image (Nightmare Fuel warning) has been associated with the video. Note the red, bloodshot eyes not unlike Squidward's. So what, right? Bloodshot eyes are used for horror, that doesn't mean that something's killing off cartoons. Enter Red Mist. It's Squidward's Suicide, except with a buisnessman telling Squidward that "the Red Mist is after you", and a lot more emphasis on the red eyes. But that's not enough evidence, right? It's just one story where the Red Mist's presence was explicitly shown. Take a look at "Rectified Anonymity", a fanfic.. Why did David have red eyes if red isn't a natural eye color? David met the Red Mist, and his sanity didn't survive the encounter. It's not a coincidence. Something is in our beloved cartoon universe, hunting its denizens, and it will not stop ever, until they are dead.

The creature from the above WMG is Forenzik.

Back when he was alive, he did the same thing to Happy Appy. Now he is dead. In any lost episode creepypasta before the Happy Appy one, he was doing it the normal way. But now that he is dead, he actually IS going into their universes, controlling them. Thanks, Yakovlev.

Jeff the Killer is a victim of HABIT.

Homicidal insanity, seemingly supernatural strength and endurance, self-mutilation? Jeff has just been a vessel for HABIT for a long time now. GO TO SLEEP RABBITS