These are just a few suggestions for those planning on writing a 'Lost Episode' pasta any time soon.
1. The "Intern working at 'X Animation Studio' has been done to death. Try to find another way to introduce the story and set up the encounter with the 'Episode' in question.
2. Try making it about a more obscure series. If it's a series that's well known, like Spongebob or whatever, then it raises the plothole that if there is a missing episode that's so violent or horrific, then why hasn't it attracted the attention of the News Media? Also, an obscure show allows the writer more creative 'elbow space', in that the writer doesn't have to take the viewer's memory or knowledge of the show into account when setting up a backstory to the 'lost episode'. If the reader doesn't know about the show or just barely remembers it, then the writer has more freedom.
3. Absolutely avoid the phrase 'hyper realistic' or any variants. The idea of a lost episode for a cartoon having extremely realistic and graphicly detailed scenes of violence has become such a cliche that it's in more troll pastas than real ones. Gore is a very cheap form of horror, and your reader will likely just find the bloodshed ridiculous rather than frightening. Try to come up with other ways of making the 'lost episode' creepy. Make them just subtle enough to be noticed. A dark shape drifting across a background can be far more effective than Spongebob chainsawing Squidward in half.
4. Read the good pastas and learn from them. Take a good look at Candle Cove for example. What do you think made Candle Cove such an effective story? Look at what made it scary to you (assuming you found it scary) and discuss it with other people that enjoyed it. I'm not saying you should make a copy of Candle Cove, I'm just suggesting you look at that story and look at the things that made it creepy (The cheap, low budget appearance concealing something sinister, puppets that look like they've crawled out of the black depths of the Uncanny Valley,childhood nostalgia and nightmares, the idea the show may have been a mass delusion or something more evil, etc.)
5. Keep the creepy shit within the video. A lost episode of a cartoon that predicts deaths, sends an evil spirit/being after you, or causes the death or suicide of anyone who watches is just fucking stupid.
6. If the story absolutely has to have something to happen to the person who views the episode, keep it something simple, like tinnitus, insomnia, headaches, triggering phobias, nausea and the like. It gets the message across that the episode is not meant to be seen without the absurdity of the suicide/ghost shit.
7. Try not to break the suspension of disbelief. We can buy that a show had an episode that wasn't aired due to offensive or frightening content. We cannot, however, buy that the episode aired once and caused several bad things to happen to the viewers without any media attention. As you write, ask yourself "Do the people in the story act like people normally would in this situation? Does the events of the pasta make sense?" It doesn't have to be completely realistic, it just has to be plausible.
8. Proofread your damn story. At least run it through spellcheck. If you're not a complete idiot, you shouldn't have to be told to do this.
Again, I'm not saying I'm some big expert on storytelling. I'm just making suggestions.