The Pixar Theory (warning: movie spoilers)

Every Pixar movie is connected.

They all exist in the same universe.  Here's how they are linked.

WARNING:  There are movie spoilers, and the concept will be confusing at first.  Hold out; it'll make sense as you read.

The first and last movie on the timeline is Brave.  Brave takes place during the Dark Ages in Scotland and is the earliest time period covered by the Pixar movies.  In Brave, Merida learns there is magic that can solve her problems, but she ends up getting her mom turned into a bear.  This magic comes from a really weird witch, who can make inanimate objects act like people.  We see her raven acting like a person.  This witch also can pass through doors and disappear.  We'll get back to her later.  Merida's mother acts like a human in bear form until the magic wears off, then she acts like a bear until the spell is taken off.

Centuries later,  the animals that the witch experimented on are breeding and are creating their intelligence and personification on their own.  We now start to see a power struggle between the humans, animals, and machines.  In Ratatouille, the rats start to work in a humans-only place: the kitchen.  They make friends with some of the cooks and cook better than the humans do. The villain of Ratatouille disappears.  What did Chef Skinner do with his knowledge that animals were quickly evolving?

Maybe Charles Muntz, the villain in Up had heard about these rumors and created collars that would harness his dogs thoughts.  He needed them to find the bird he obsessed over and comments on how many dogs he's lost while trying to find the bird.  When Dug and the other dogs are set free, we can tell that the animals are starting to resent humans.  However, humans are unaware of this and are developing more technology to harness the power of animals.  They begin the industrial revolution hinted at in Up.  Carl is forced to sell his house to a corporation expanding the city.  Who is responsible?

Buy-n-Large. (BNL)

The corporation that runs everything by the time we get to Wall-E.  This organization is also hinted at in Toy Story 3.  Back to the animals, though.  In Finding Nemo, the creatures of the ocean save Nemo from the humans.  Dory's lack of short-term memory contrasted by her ability to read and speak to whales shows that the fish are evolving in different ways.  Now we'll start with the machine side of things.

In The Incredibles, Syndrome, the villain, uses technology to beat up Mr. Incredible.  Syndrome creates the omnidroid, which eventually turns on humans and heroes alike and kills them.  But why would machines hate people?

Enter Toy Story.  Humans discard toys that obviously have feelings.  The toys deal, but get fed up with it later in the trilogy.  But how can they draw power?  Syndrome told Mr. Incredible about Zero Point Energy, which is the electromagnetic energy that exists in a vacuum.  This is how the inanimate objects gain energy and personification.

During the Toy Story trilogy, the super-humans have died and humanity is vulnerable.  Yet we don't see any animal or machine uprisings.  We do, but not in the way we think it will happen.  The machines create BNL.
The machines only know constant fulfillment of their needs, so they model BNL on that.  BNL creates the industrial revolution and the pollution of Earth.  We know the machines win because Cars takes place after all the humans have left Earth.  As a last attempt to save the human race, humanity is put onto Axiom, the giant space ship in Wall-E.  Humanity is completely dependent on machines for their basic needs, and machines use the humans as their energy source. Meanwhile, machines are left to take care of Earth and run things, explaining why human landmarks and traditions still exist.  In Cars 2, the cars travel around the world and there is an oil crisis.  Allinol, the 'clean' fuel corporation, is created to turn cars away from alternative energy sources and kills off many of the cars.

Back to Wall-E.  Wall-E is the only machine left because of his fascination with humans and animals.  He remembers a time when humans, animals, and machines lived in peace.  That's why he liberates the humans.
Once the humans rebuild life on Earth, they plant a tree.  A tree that grows to look surprisingly like the central tree in A Bug's Life.

The reason there are no humans in A Bug's Life is because there aren't many left.  Bugs and birds have returned and the bugs have created cities with ads, bars, and inventions.

Now onto Monsters.  Humans, animals, and machines interact positively now, creating a new species: monsters.  The monsters are the mutated animals left from when Earth was abandoned.  They have cities, and even universities as seen in Monsters University.  The humans are all gone now, which is a problem for the monsters as they need humans for energy.  The doors aren't to visit alternate dimensions, though.  The doors go back in time, when humans existed.  What happens to Boo, the toddler who befriends Sully?

She's the witch in Brave.

Boo remembered that doors were key and uses the will-of-the-wisps to create time doors.  Hints of Sully are everywhere in the witch's workshop.  There's even a carving of him.  Boo is obsessed with wood because she found out that wood has the magic to travel in time.  That's why the doors in Monsters Inc. are made of wood and the banishing door is made of metal (so the monsters can't get back out).  She turns people into bears because she is trying to figure put where Sully came from.

That is the Pixar Theory.  Hope you enjoyed it!

Source:
http://jonnegroni.com/2013/07/11/the-pixar-theory/
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