The Legend of McDonaldland Loch
You guys are all familiar with the Spongebob Red Mist creepypasta, right? It's the one about a lost episode of Spongebob in which Squidward kills himself and is, essentially, a variation on the pasta Squidward's Suicide. While the legend itself has been debunked countless times, it is worth noting that this particular story was, in part, based on a true story. In a now deleted animationnation.com forum post from 2005, a user named JebJoker recounted his experience of working as an intern for Klasky Csupo in the early 2000s (primarily as an inbetweener for the show The Wacky Adventures of Ronald McDonald), during which time he witnessed a particularly disturbing incident involving a fellow animator.
Andrew Skinner was a Scottish artist and animator hired by Klasky Csupo exclusively for the Wacky Adventures episode “The Monster O' McDonaldland Loch”, as both serving director and animator, due to his Scottish heritage, in order to give the episode a genuine Scottish feel (given that the entire episode takes place in Scotland and is a parody of the tale of the Loch Ness Monster). The episode's production ran smoothly until an employee noticed a strange interference while reviewing a pre-release cut of the cartoon. What at first appeared to be simple static interference, upon closer inspection, was found to be a series of distorted, gory images taken from Ogrish.com and other, similar sites. It was later discovered that, not only had a large number of gory images been snuck into the episode via single frames, but that some of the background textures had actually been made up of scrambled, edited versions of said images.
The production team was furious, as this meant that the episode would have to be delayed to give the animators enough time to fix it up and remove any and all of the offending images within. Andrew Skinner would later come forward as the culprit, stating 'artistic expression' as his reasoning; he was immediately suspended without pay. The episode proved so full of obscene images that it was delayed to the point where the in store promotion was concluded, leading to it only being sold online (and in limited numbers) under the altered title “The Legend of McDonaldland Loch”. JebJoker has suggested that, while most of the unacceptable content had been removed, some remnants may have slipped through the cracks and made it into the official release. Andrew Skinner's exploits would later be taken to the extreme in the aforementioned Red Mist story, which falsely claims that he was a murderous member of the Spongebob production team.
The Legend of McDonaldland Loch has proven extremely difficult to track down, although at least one copy has been accounted for. In late December of 2014, a member of 4chan's /co/ board revealed that he was in possession of a copy, providing photos and screenshots to back up his claim. The user stated that he intended to rip a copy of the tape and share it around online before selling it on eBay. However, within a short period, another anonymous user posted in the thread that they were willing to purchase the item for a whopping $15,000, so long as it was kept under wraps and off the internet. While many have discounted this offer as a hoax, there are some who believe that Andrew Skinner himself was the one who offered the large sum to keep his now-tarnished work from ever seeing the light of day. The tape owner has since gone quiet, ceasing to provide updates on the situation for several months in a row; it is theorised that Andrew Skinner made good on his offer and that the OP has gone quiet as a result. As of this writing, the tape remains totally unaccounted for, as does the episode itself.