Essentially internet horror stories or a myth passed around other sites, to frighten readers and viewers. The word, "Creepypasta" comes from the term, " copypasta ". An internet slang term for a block of text that gets copied and pasted from website to website. Creepypastas are sometimes are supplemented with pictures, audio or video footage related to the story. Typically with gory, distorted or, otherwise, shocking content.
Suicidemouse.avi was the grandfather of all lost episodes. It showed Mickey Mouse walking down a endless street with random piano keys playing in the background. The video gets more distorted and music turns static. See for yourself.

Also, Sonic.exe is a very well known Creepypasta. There is even a clone of the game to download. Although it's it well done, the clone will never have the same fear factor as the story did.

Lastly, Slender Man was introduced in 2009 in the Something Awful forums. Slender Man was not well know untill 2012 when Mark Hadley released, "Slender:The Eight Pages".
by DiddleMcGibberson March 23, 2014
Online stories that will haunt the things that haunt you. Things you read during the day thinking "this'll be fun" and then wish you hadn't when night comes around.
"Fuck I read creepypastas today. Good bye sleep."
by WaffleGhost April 16, 2014
Creepy stories that float around on the Interwebs.
Kate: I heard that if you say "Bloody Mary" 3 times into a mirror, a hook will appear on your car door.

Rob: No, dude. That's just some creepypasta.
by howtocookhumans March 27, 2008
Creepypastas are a bunch of fictional characters such as Jeff the Killer, Eyeless Jack, Slenderman, Sally, etc... The characters where originally just creepy stories like all the other creepypastas but they were taken over by fangirls.
Person 1: Hey bro, did you read that new creepypasta I told you about?
Person 2: Yeah, I heard it from Mr. Creepypasta on youtube, it was so creepy!
by TaylorGarciax February 19, 2015
Made up ghost stories and fake lost episodes to famous shows that spread around the interwebs.
Dude: Watch out for Slenderman! He might come and get you!

Me: Dude, thats just a creepypasta
by Creepypasta May 12, 2012
This word means, in this sense, stories and thrills that float around the world wide web. Famous creepypastas include: Jeff the Killer, the Russian Sleep Experiment, Slender Man, and more!!! Other Creepypasta include, but not limited to: Smile.exe from My Little Pony, Squidward's Death, Sonic.exe, 1dollar.wav, and many more.
Guy 1: Finnegan, why does Pinkie Pie have a demonic smile?

Guy 2: Don't worry, O'Lafferty, that's jus a creepypasta.
by pricker75 May 20, 2015
A story on the Internet of events that are very important for people to know about because of how horrifying and creepy they are. It's important that people know about the events that have transpired in these accounts, so the people telling us about them make sure to use so many grammatical errors, tense swaps, and misspelled words that they are virtually unreadable.
Man 1: (reading) "My whole family is afraid of me now. I can't kill them. Since I only know of Emily's death. I want no one to oppose me. No one to break my glass. This, soon, will become the society. I will even make Wily's Society look like a nonexistent heaven. I already made a big slaughter just like after the fatal battle between the sons of Light."

..........What the hell does that mean?

Man 2: It's creepypasta. If these people were good at writing scary stories, they'd wouldn't have put them on a creepypasta web site.
by Thu Kang-A-Lang April 19, 2015