Perpetual Testing Initiative
The Perpetual Testing Initiative is a gamemode and campaign released on May 8th, 2012. It introduces the concept of multiple alternate universes, simply shortened as "the multiverse." Set entirely on testing chambers created by the Portal 2 community on the Steam Workshop, the player once again has to fulfill the role of test subject - this time as silent stick figure Bendy.
The test chambers in the DLC are completely user-generated, using the simplistic in-game testing editor "Puzzle Creator", a much simplified version of Hammer.
It appears that Cave Johnson still lives in the multiverse and as healthy as he was before he was poisoned after contacting Moon rocks in an attempt to create Conversion Gel in the main Earth, as Bendy can hear Johnson talking to him from a microphone as he navigates the test chambers. Also, every Earth in the multiverse results with GLaDOS being abolished after she tries to flood the Enrichment Centers in the various Earths with deadly neurotoxin.
Introductory Video
Known Universes
The Prime Universe
The universe that Bendy and one Cave Johnson, known as Cave Prime, are from, featuring "Earth-1," aka "Terra-Firma-Prima." It is implied to be a different universe than that of the main story, as Cave is still alive, does not seem to be ill, and mentions shutting down the GLaDOS project after what happened to Pure Intellect!Cave. In addition, Cave's assistant is Greg, rather than Caroline, although he could simply have two assistants.
Cave Prime indicates the communications from this universe by initially saying the phrase "chariots," and later by "chariots chariots," after discovering another Cave who is simply fond of saying "chariots" in his sentences.
It is possible, but unproven, that this universe consists of only stick people, as Bendy himself is a stick man. It is equally possible that Bendy was pulled from another universe.
The Birthday Universe
Everyone shares a single birthday. Upon reaching ninety-eight, the government-mandated maximum age, they are promptly euthanized by an Ethnological Redundancy Associate. In addition, this Earth is implied to have limited resources, and food seems to consist only of "nutrient paste."
When signing off, Birthday!Cave includes his age (fifty-one). It's unclear if this is voluntary or mandatory.
The Blapature Universe
Cave Johnson has bought-out and taken over Black Mesa, coining it "Blapature Mesa." Blapature!Cave shuts down the research Black Mesa was doing that inevitably lead to the alien invasion of the Half-Life / Portal universe, and scolds the employees for thinking that it would be a good idea. This, and the fact he bought out Black Mesa in the first place, imply that this Cave is one of the few who is actually a good businessman.
The Blark-Barg Universe
In this universe, Caroline is replaced by Blark-Barg, a creature who produces "seeds that germinate and detach from her exoskeleton at high speeds in search of human hosts." She is kept behind glass.
The Body Snatcher Universe
A reference to The Body Snatchers.
An alien has been "body-snatching employees and spawning Communist replicas." This universe's Cave is unbothered by it, as it doesn't seem to be a real threat.
The Cat Universe
Everyone, or at least Cave Johnson, is presumably a cat. Cat!Cave speaks in the exact same tone-of-voice, but only says "meow."
Funnily enough, Cave Prime refers to both himself and Dark!Cave as "cats" at one point.
The Creepy Universe
Creepy!Cave seems to have an obsession with hair, feet, and eating both of these things. The ambient noise of dripping water in his communications implies that Creepy!Cave may be in a literal cave.
The Dancing Universe
Everyone is required by law to never stop dancing, even while testing. This is enforced by the Dance Police. Dancing!Cave practices tap dance, specifically.
The Dark Universe
In this universe, people breath methane, eat only asparagus, and have a portal gun which can portal on any surface.
Dark!Cave has the same idea as Cave Prime, and uses the multiverse to test inside of Cave Prime's chambers. He enjoys messing with Cave Prime, doing things like sending in a frozen block of urine, which is extra effective considering this planet's diet (see above).
At one point, Dark!Cave attempts to confuse the player by impersonating Cave Prime, even adapting a form of Cave Prime's codewode: "chariots chariots chariots." He also attempts to persuade the player to lead him to the Moneyverse, rather than Cave Prime, with the promise of a promotion, double asparagus rations, and plenty of methane gas. When two moneyverses are discovered, they decide to split the findings, meaning that they're both wealthy enough to no longer need to test in alternate universes.
Dark!Cave is the only known Cave to directly contact another Cave, Cave Prime. They are nemeses with mutual respect, as they are the only ones who truly understand each other. Also, Dark!Cave's name is a pun -- that is, dark cave.
The Gas-Finding Universe
The goal of Aperture Gas-Finding Science is to find gas. Gas-Finding!Cave states that if they meet their quota, they will "don their bondage gear, fuel [their] death cars, and drive around in circles, whooping it up and shooting arrows at people." This implies that by "gas" he means gasoline, and that this universe is a parody of Mad Max.
The Godzilla Universe
Aperture has hatches a large quantity of Godzillas. They prepare for attack, only to find that all Godzillas instinctively head towards Tokyo.
The Hobo Universe
Everyone is, predictably, a hobo. Aperture Science is called the Aperture Hollow Science Jungle, and Hobo!Cave refers to himself "Michigan Slim" Cave Johnson, the Hobo King.
The Light Universe
Despite what the name implies, this is not the opposite of the Dark Universe.
Aperture Science has successfully transformed all of its employees, and possibly the rest of the world, into beings of pure light. Unfortunately, this wasn't their goal; they were aiming to become pillars of pure salt, a biblical allusion of sorts. In Light!Cave's words, "so salty."
The Mantis Universe
Everyone is a praying mantis, yet somehow still capable of speech. Mantis!Cave performs an experiment involving injecting other mantises with human DNA. It yields similar results to Human!Cave doing the opposite.
The Mantis-Men Universe
Not to be confused with the Mantis universe.
The mantis-men from Cave's experiments storm the facility, take it over, and presumably kill all of the humans.
The Matriarchal Universe
The Earth is run by the Supreme Council of Matriarchs, who have eradicated all men. Cavina Johnson, this universe's Cave, insists that she and her assistant, Sally-Sue-Greg, are women, despite accusations otherwise. It's strongly implied that they are actually men, but are trying to avoid the same fate as the others.
Apparently, conflicts in this universe are resolved with sympathy cards and discussions about feelings.
The Money Universe
Also known as the Moneyverse. The Earth is made entirely out of US Dollars. Cave Prime speculates there to be infinite moneyverses; however, judging by Greg's reaction to this Cave's "math," this may be false.
There are two known versions of this universes in existence.
The Nice Universe
The Cave from this universe is much nicer than most other Caves, and seems to genuinely care for and appreciate his employees. Nice!Cave also has a tendency to insert the word "chariots" into his sentences for seemingly no reason, prompting Cave Prime to change his code-word to "chariots chariots."
The Octopus Universe
Everyone is an octopus. Cave Prime uses this universe as an example of stealing outsourced test chambers.
The Overseer Universe
Cave Johnson is literally the entire planet. He refers to himself as the Overseer.
The Paranoid Universe
Paranoid!Cave has been trying to prepare for the event of cross-universe invasion, but his warnings were ignored and dismissed as unfounded paranoia. Ironically, this universe has now actually been invaded by beings from another universe -- that is, the players. Paranoid!Cave adopts an I-Told-You-So attitude.
The Paranormal Universe
Aperture is known as Aperture Paranormal, and seems to be focused on learning the secrets of magic rather than conducting scientific research. Paranormal!Cave hosts a "tiny but powerful demon who lives in a secret place in [his] mouth," a reference to The Shining.
The Peanut Universe
Humans breathe peanut dust, and oxygen is a common allergen.
The Prison Universe
In this universe, Cave Johnson is the warden of the Terra-3 Penal Science Colony. "Terra-3" implies that this is the third universe, if Earth-1 is to be considered the first.
At one point, most of the prisoners escape due to the Science Colony lacking physical doors. This also results in Warden!Cave getting shivved multiple times and dying.
The Pure Intellect Universe
Cave Johnson has successfully uploaded his consciousness onto a computer, becoming Pure Intellect!Cave. Unfortunately, gaining ultimate knowledge gets boring very quickly, inspiring Pure Intelligence!Cave to rewrite the entire literary canon of the human race to include things like moon bases and " busting ghosts" -- at least until he gets to Wuthering Heights and gets bored of that, too. Soon, the less-than-sane Pure Intellect!Cave finds inspiration from Hercules (somehow) and decides to destroy Aperture and everyone in it, prompting Cave Prime to abandon the GLaDOS Initiative for fear of similar results.
The Propaganda Universe
Every surface of Aperture Science is coated in subliminal messaging to "motivate" employees and test subjects. There is a pair of sunglasses which allows the wearer to see these messages, and Propaganda!Cave is not happy about it.
The Rattman Universe
Doug Rattman is head of Aperture Science, and Cave Johnson is the former junior claims representative, and also implied to be much younger.
Upon being fired, Young!Cave sneaks into the recording office and accuses Rattman of embezzling funds. Knowing Cave's tendency to enhance the truth, this is to be taken with a grain of salt.
The Ritual Universe
In this universe, Aperture is known as Aperture Rituals. The ritual in question is an "ancient mating ritual etched in a monolith by the Elder Monks to forestall the end of days." It involves, in Ritual!Cave's words, making love to a giant bird.
The Robotacop Universe
A blatant parody of Robocop.
This universe's Cave purchased several corpses with the intent to turn them into half-man half-machine police officers as part of the Android Law Enforcement Initiative. He names his creations, well, Robotacops. The reason that the Robotacops must be tested before going on-duty is to ensure their mental stability.
There is a glitch in the Robotacop software that may give them "tragic flashbacks of [their] former live[s]." This Cave ensures the player that the memories are actually "a real-time feed of [his assistant] Greg's current life," which is very sad.
The Sentient Cloud Universe
This version of Earth is governed by a single, ominous, Sentient Cloud. The Cloud demands worship, forbids cameras, and consumes anyone who opposes it, including anyone not partaking in the full mandatory moment of silence to honour its glory.
All hail the Sentient Cloud.
The Soylent Green Universe
The only thing known about this universe is that Soylent Green is a real thing, and it is very expensive. As such, Soylent!Cave has requested the cafeteria stop serving it, no matter "how good people tastes."
The Space Universe
Aperture Science has moved its location to a satellite orbiting Earth. This is unbeknownst to several employees, who form "adventuring parties" to try and uncover the facility's "conspiracy," which is simply that its now in space. Space!Cave becomes exasperated by this behavior, as he states repeatedly that the secret is literally that they are in space, and it was never a secret to begin with.
The SuperMaxLantis Universe
Atlantis not only exists, but is a high-security prison where the President is being held hostage. Science facilities across America have "been tasked with producing a Tough Guy capable of breaking into [it]." SuperMaxLantis!Cave insists on himself being that Tough Guy, and so requests the player send in a positive reference for him.
The Telekinesis Universe
Certain tests subjects were given psychic powers as part of the Telekinesis Incubation Program. The tests subjects in question soon began to use their powers to explode people's heads.
The Timmy Universe
A sick child by the name of Timmy encourages the player to solve the test in hopes that he might overcome his condition. He doesn't.
The Tiny Universe
Aperture has developed the technology to shrink things down to the point where they can be transported into Cave Johnson's bloodstream. This includes the player's current test chamber, as well as Cave's car keys.
The Trucker Universe
"Big Box" Cave Johnson is a truck driver, and speaks in a southern accent. He is also still in charge of conducting tests, whether at Aperture Science or a trucking equivalent. Trucker!Cave's accent seems to be fake, as he returns to his normal voice to address his test subjects.
Possible Universes
The Alternate-History Universe
A proposed universe where the Greeks won World War II. Cave Prime brings this up in case the player encounters a test chamber filled with urns.
The Inside-Out Head Universe
Self-explanatory.
The (other) Money Universe
In this universe, the Earth is made out of Pesos, rather than USD.
The Slow-Light Universe
Another proposed universe in which light moves slower. Cave Prime warns the player that moving faster than light will apparently send them backwards in time.