Alright, here's something that's a bit similar to a Creepypasta in feel. I know for a fact this scene actually exists, but it wasn't very interesting
Remember the show Catscratch? This scene was in "Scaredy Cat", the Halloween episode with the aliens.
At the scene where they're in space, Gordon talks to his brothers about how evil has come to cocoon them on Halloween. While this is happening, a small, boxed frame of Hovis dressed up as a rabbit (this is a still shot from another episode) pops up for a few seconds. It's really odd and random; I'm guessing someone on the crew accidentally spliced a part from one episode into another.
I saw this part back when I saw the episode on TurboNick in 2005. However, when I saw a Mega.nz
rip taken from Nicktoons Network, it wasn't there. Maybe they scrubbed it out later airings.
Here's proof that it exists:http://www.tv.com/shows/catscratch/forums/subliminal-message-in-scaredy-cat-20036-199391/