The PC is a mechanism for the storage, retrieval, rearranging, and release of Pokemon captured by the player. In Twitch Plays Pokemon Red and Crystal, the erratic nature of the stream combined with the PC's ability to irretrievably release Pokemon have made it one of the most unpredictable and dangerous things for the Mob to encounter.
The PC and its storage system and network were created by Bill, adding yet another level of distrust and malignity to the researcher's record in the eyes of the Hivemind.
The Dangers of the PC
The greatest danger and most notable part of the PC to TPP lore is the Release command. Released Pokemon are removed from the game completely, irretrievably, and are generally considered to be dead. This results in a - quite logical - fear of losing beloved, powerful, or important Pokemon to a few seconds' mistaken command; a minor danger in a single-player Pokemon playthrough, where the player is likely to begin mashing B as soon as they see what they've accidentally selected, but an absolutely devastating and very likely hazard that has reared its head in TPP many times in all three games thus far.
The greatest danger of the PC lay in the Red playthrough, where the Release command was situated at the main menu of Bill's PC, along with "Withdraw Pokemon", "Deposit Pokemon", and "Change Box". A simple slip of the cursor could result in the Mob anarchically scanning through the stored Pokemon and releasing any it selected, and cancelling out could result in completely leaving the PC (and thus aborting whatever cause had brought us to it in the first place) or starting the process over from the beginning, with equal risk.
In Generation II's Crystal playthrough, the threat was slightly mitigated. The Release command had been removed from the main PC menu and relocated to the menu brought up when a Pokemon in the PC is selected, along with "Withdraw/Deposit", "Stats", and "Item", meaning that withdrawing and/or depositing a Pokemon could usually be accomplished with a simple spamming A once the desired creature was selected. However, delayed inputs, mistimed aid, or deliberate trolling could - and did - result in the release of Pokemon, especially when fueled by the "Release the Gator" campaign that ran in the Twitch chat for some time.
The threat of the PC is not lessened by desire to use the PC for other methods such as retrieving items from Red/AJ's PC; a misstep can easily lead to being mired in Bill's PC, which in turn can lead to accidental releases. The only safe method to access Red's or AJ's PC to retrieve or store items was to do so from their own personal terminal, in Pallet Town and New Bark Town respectively, since these machines did not connect to Bill's network.
In Season 2, the danger the PC posed was mitigated slightly. Although the Red Anniversary saw the most victims fall to the PC, Leech King, one of its supposed victims, is believed to have actually survived, merely escaping and going into hiding. In Touhoumon, the PC's ability to sacrifice Pokémon was nullified completely, the only attempt to release a Pokémon failing. While the PC regained some of its ability back in Randomized Alpha Sapphire, once again a Pokémon managed to merely escape, this time Flygitt managed to escape.
Red: The Flareon Debacle and Bloody Sunday
In TPP Red, the first major PC event was situated around the receiving of an Eevee in Celadon City. With the stream divided as to what should become of the Eevee - some wishing to evolve it into a Vaporeon and use it to provide Surf for the party, others wanting to reserve that spot in the group for the Lapras they would be receiving later - the Mob nevertheless entered Celadon Department Store and emerged with a Fire Stone, the least-desired of the three Gen 1 evolutionary options. In addition, they managed to use it successfully, evolving Eevee into Flareon. The Mob then decided they wished to get rid of the newborn Flareon, christening it the "False Prophet". The process of releasing it was costly, however - Abby and Jay Leno were released and The Keeper boxed and nearly released before Flareon was finally disposed of.
Much later, on Sunday, February 23 (Day 11), after capturing Zapdos at the Power Plant, the Mob attempted to withdraw him to add to their active party; however, the process turned out to be long, complex, and extremely lethal, resulting in no less than twelve Pokemon - among them active party members Dux, DigRat, and Cabbage - being released before AA-j was successfully added to the party.
Crystal: "The Gator Wars" and associated events
- Main article: The Gator Wars
Due to LazorGator (Gen 2's starting Pokemon and AJ's most powerful team member) highly overleveling the rest of his party, complaints arose early into the Crystal playthrough of him being overpowered and/or an experience sponge that prevented the rest of the party from gaining levels and evening out the experience spread. This, combined with the desire of some to see more death/release-based drama in the vein of Gen1, lead to a series of attempts by a sizable faction of the stream to "Release the Gator" - to deliberately deposit LazorGator in the PC and then either release him or go training without him, forcing the game to continue without him in the party as a crutch. This was attempted no less than three times, resulting instead in the release of a handful of other Pokemon, including Prince Omelette and Colonel N, after which the faction either faded off or lost interest, as later encounters with the PC led to larger numbers working to ensure the Gator's survival.
The PC interface in Emerald is greatly revamped from the first two generations, with a format that persists through all of the future generations - rather than having the Pokemon in a vertical list, they are arranged in rows and columns. Like in Crystal, the Release command is located on the Pokemon itself, but it is near the bottom-middle of the list, making it much harder to access. This new arrangement, in addition to the drag-and-drop Deposit menu, makes it very easy to place Pokemon into the PC, but very difficult (at least, in Anarchy) to take them out or Release them. While this does seem to prevent accidental Releases, it also makes it difficult to change the party lineup without losing large numbers of team members into the PC "prison" or "Purgatory", and makes it troublesome and time-consuming to retrieve them.
The PC system in Emerald is managed by Lanette, a former student of Bill, rather than the man himself; it is unknown what her position or allegiances toward Bill or A are as of yet.
The first notable encounter with the PC in Emerald was when A initiated contact with the machine to retrieve a Marill she had caught, intending to use it to battle the Rock-type Gym Leader Roxanne. Unfortunately while she did successfully retrieve the Marill, the entirety of her Pokemon otherwise were deposited. She was eventually able to withdraw Dogeyena & Zexy before leaving the PC. Such exchanges have happened a few more times since, with Pokemon usually being deposited in multiples then one or two at a time withdrawn.
The PC is not without danger though even now, and it is possible to still release Pokemon: Zexy was accidentally released while the Mob was rearranging their team during their many attempts to defeat Wattson.
The PC in Lore
Of all the creatures, people, and objects in Pokemon, few have received as much lore, alternative interpretations, and outright fear as the PC.
Some common depictions of the PC simply manifest it as a destructive but inanimate force of nature, more beast than entity. Whether due to hunger or some innate destructive urge, its purges of the Pokemon stored within are due to instinct rather than malevolence.
Others depict the PC as a foul deity, an Elder God that can only be appeased by sacrifices and bloody offerings, resulting in any attempt to elicit its aid potentially reacting in it demanding the blood of the innocent (and, in some cases, the not-so-innocent) before it will cooperate with those who remain. Perhaps the amount of losses with each series of casualties could be construed as a sort of "Devil's Price" - for example, banishing the false prophet Flareon simply required the price of Abby and Jay Leno to sate its blood thirst, but the far more powerful and far more desired Zapdos elicited the immensely more taxing price of Bloody Sunday.
Added to all of this is the fact that the PC system is managed by Bill - directly in Generations 1 and 2, and indirectly through apprentices and proxies in later generations - whose connection to the Eevee line has painted him as a villain (perhaps even the greatest villain) in TPP lore. It's difficult to say, really, whether the destructive potential of the PC caused Bill to be viewed as a demonized figure, or Bill's own poor reputation and connection to the False Prophet of TPP Red led to part (though likely not all) of the PC's depiction as a horrifying or malevolent monstrosity. More than likely, it's a combination of both factors.
What is universally agreed on is that the PC is a danger to all, save perhaps in a particularly well-managed Democracy, and that only in the most urgent situations of need should its aid be sought out.
In Emerald, frequent trips to the PC - combined with the compex and time-consuming process required to retrieve Pokemon from within and the (thus-far) lack of any Releases despite multiple PC uses and multiple exchanges of entire parties in and out of the machine - have resulted in some interpretations of A being very interested in computers, having an alliance with the PC as she does with The Voices, or for some reason otherwise lacking the fear and dread of the machine that pervaded Red and AJ's stories.