A webcomic by Andrew Hussie, professional troll.
Tells the story of John Egbert and his friends as they play a videogame. Unfortunately, things aren't as they seem, and things quickly evolve into a series of events that have to be seen to be believed.
A massive, temporally knotted story involving shaving cream (how can it be so flammable?), Nic Cage, juggalos, jpeg artifact, eldritch beings, a man with a cueball for a head, absolutely no pumpkins, buckets, murder, mayhem, and Betty Crocker.
Brought into East by GeorgeAspesi, where it quickly spiraled out of control as more and more people began reading it.
(Note: The HomeStuck fandom is second only to the Touhou fandom in tenacity, creativity, and insanity. When Andrew Hussie went on a brief hiatus prior to SDCC, part of the fandom convinced another part that a Homestuck anime existed using fake screen caps. You have been warned.)
Can be read [here].