In Pixar's Monsters films (Monsters Inc. & Monsters U), the monsters make special doors, which connect to an Earth like ours. They then use these to harvest scream energy from Earth children by scaring them. It's clear that the Monsters planet isn't Earth, these are magical/technological doors that get them from the Monsters' planet to Earth. While the door-making process is just barely touched upon in Monsters U, I'm hoping there's some interviews or other out of film details on this technology.

When the Monsters make one of these doors, are they able to connect them to someplace other than Earth?

  • 1
    Maybe I've missed something, but where has it even been established that the monsters are actually the ones making the doors? We've seen their storage, use, destruction, and repair. But to my knowledge (though I haven't yet seen Monsters U) we've never actually seen a door made from scratch.
    – Iszi
    Commented Jul 11, 2013 at 21:21
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    @Iszi Monsters U shows this, as the question states.
    – user1027
    Commented Jul 11, 2013 at 22:01
  • 1
    Ah, I must have glazed over that. My bad. Definitely should catch up on that film - my daughter already has.
    – Iszi
    Commented Jul 11, 2013 at 22:13
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    This postulates that the monsters are time traveling: jonnegroni.com/2013/07/11/the-pixar-theory
    – Mark
    Commented Jul 13, 2013 at 1:56

2 Answers 2


Given the information we have seen in Monster's Inc. and Monster's University, we cannot make any assumptions about whether the "Door bridging technology" would be capable of reaching distant planets (assuming they had doors or suitable portals to connect to).

  • In and of itself, the Door bridging technology appears to be highly advanced (by Human standards) but we simply don't know enough about HOW it works to determine its range, efficacy or limits in target-choosing capacity to know if interplanetary or interstellar ranges are within its capacity.

Since it is implied that Monstropolis IS on Earth we must first establish the parameters for interactions between the two groups:

  • At some point in the past, Monsters were forced to seek refuge away from Humanity and have hidden themselves on an island Humans are not able to find. Humanity has come to accept Monsters are a myth and as such remain unaware of them in the modern day. Why the two factions separated or how monsters came to exist in the first place is never discussed.

  • What is known (at least by all Monsters) is that Monsters and Humans never mix and it would seem today Monsters both fear discovery by Humans and have created a mythology to ensure Monsters never desire to freely mix with Humans, i.e. the myth of human children (and by proxy, Humans in general) are toxic and dangerous to Monsterdom.

  • Given that what we have seen of the Human world appears to mimic our own, Monstropolis either employs sophisticated stealth technology capable of hiding it from Human technology like spy satellites, or it exists in such a way it is only capable of being reached using the Door technology.

  • Why did the Monsters create their unusual technologies in the first place? Technology development is an answer to a problem in a society. Why did Monsters create a technology to harvest screams (fear) to power their society? Was the technology or ability to harvest fear unique to Monsters?

  • The ability to harvest and convert "Scream" and later "Laughter" as viable energy sources indicate the Monsters have a level of technology far beyond Human norms. Neither has energy potential value in the Human World.

We are forced to make assumptions about the door bridging technology based on its specific and highly regulated use in Monstropolis.

  • The Door technology is only used to reach the Human World. It isn't used to reduce travel time within Monstropolis. There is mass transit including busses, trains and personal cars. This indicates either the technology is too energy intensive for local work, requires sophisticated targeting, or is absolutely only able to reach target doors in the Human World.

  • This raises a few other questions such as: Why are humans unable to find the Monster's World? Such advanced technology surely has, if nothing else, a heat and/or light emission capable of being seen from orbit. So how does Monstropolis stay hidden from Human's curious nature?

What do we know of the Door Bridging Technology? Turns out, not much:

  • The Door technology comes with three parts. The quantum-entangled door, the bridging technology and the targeting technology.

    • A door is created and linked specifically to a particular door.

    • It is implied each door is linked to a certain door for a time until that door is later destroyed and shredded. Shredding happens when a door has been compromised or when a child no longer produced screams, presumably as they aged.

    • Monster's Inc indicates a door remains linked as long as every piece can be found and put back together.

The Monster technology that is never explained in detail is:

  • the targeting system (how are doors with children of the right age found?) How is the signature for the Bridging Door, linked to the Child's Door?

  • the bridging system, is the technology in which the Door is placed to open a link between the two worlds. We must presume the creation of the link uses less power than it is able to recover, because if it didn't, they would use something else instead.

  • We are never taught or told what a unit of Scream or Laughter is equal to in the Human World in terms of horsepower or ability to do work. (Insert your preferred unit of energy here) So we don't know if the Monsters are sitting on an energy gold mine or just gathering enough energy to keep themselves and their society hidden from Humanity.

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    I wonder if you could provide some references to the implications that Monstropolis is on Earth. Or is that a spoiler for Monsters U?
    – ardent
    Commented Jul 11, 2013 at 22:00
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    @ardentsonata That was posted earlier today, on my other Monsters question. Apparently a DVD extra established that.
    – user1027
    Commented Jul 11, 2013 at 22:02
  • The short film "Party Central" establishes that doors can be used within the monster world albeit via a connecting bedroom.
    – Valorum
    Commented Apr 20, 2016 at 22:29

The Monsters are almost certainly a space-faring race, or one that had space-faring capabilities in the past. The entirety of their civilization seems to encompass a single city, meaning that they came to that world at a later date with a technological base intact. A population that evolved on that world would have grown to encompass all habitable parts of that planet in the course of their evolution and civilization, and there is no evidence of them being pushed back to a single city afterward through circumstances like environmental catastrophe or nuclear war. The morning they walk to work it's bright and shiny, and street vendors are selling fruit/vegetables as if they have an agricultural system in place.

This suggests to me that yes, they can make doors that connect to other worlds, assuming a compatible door exists there. It might even be the method by which they first came to the world they currently reside on.

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