imma leaving for a vaca 2moro so i wont be posting for 2 weeks aftter now. i also noticed that the link in a post i made a little while back doesnt work, so here it is again: http://mashable.com/2013/07/12/the-pixar-theory/ and also i may as well just copy the whole thing below, but those too lazy to enjoy the full awesomeness of this, heres a link to a very short timeline which gives just a very basic overview: http://jonnegroni.com/2013/07/15/the-pixar-theory-timeline/

The Pixar Theory: Every Character Lives in the Same Universe

By Jon NegroniJul 12, 2013

Jon Negroni spent one year untangling the secret world hidden deep within Pixar films. This thesis (printed in full below) originally appeared on his personal blog and quickly became a viral sensation. Negroni continues to update his post based on interesting feedback from readers.
Several months ago, I watched a fun-filled video on Cracked.com that introduced the idea (at least to me) that all of the Pixar movies actually exist within the same universe.
Since then, I’ve obsessed over this concept, working to complete what I call “The Pixar Theory,” a working narrative that ties all of the Pixar movies into one cohesive timeline with a main theme.
This theory covers every Pixar production since Toy Story: A Bug’s Life, Toy Story 2, Monsters Inc., Finding Nemo, The Incredibles, Cars, Ratatouille, Wall-E, Up, Toy Story 3, Cars 2, Brave and Monsters University.
Every movie is connected and implies major events that influence every single movie. Here we go.
[EDITOR'S NOTE: All updated text in italics indicate new edits made since the original version published, based on interesting reader feedback.]
Brave is the first and last movie in the timeline. Obviously, this movie about a Scottish kingdom during the Dark Ages is the earliest time period covered by the Pixar films, but it’s also the only Pixar movie that actually explains why animals in the Pixar universe behave like humans sometimes.

In Brave, Merida discovers that there is “magic” that can solve her problems but inadvertently turns her mother into a bear. We find out that this magic comes from an odd witch seemingly connected to the mysterious will-of-the-wisps. Not only do we see animals behaving like humans, but we also see brooms (inanimate objects) behaving like people in the witch’s shop.
We also learn that this witch inexplicably disappears every time she passes through doors, leading us to believe that she may not even exist. Don’t get ahead of me, but we’ll come back to Brave. Let’s just say, for now, the witch is someone we know from a different movie in the timeline.

UPDATE: Some readers pointed out that the animals in Brave gradually regress back into an animal state, disproving the idea that this is the source of animals acting like humans. My rebuttal is simple. They regress because the magic wears off. Over time, their evolving intelligence grows naturally.

Centuries later, the animals from Brave that have been experimented on by the witch have interbred, creating a large-scale population of animals slowly gaining personification and intelligence on their own.
There are two progressions: the progression of the animals and the progression of artificial intelligence. The events of the following movies set up a power struggle between humans, animals and machines. The stage for all-out war in regards to animals is set by Ratatouille, Finding Nemo and Up, in that order. Notice I left out A Bug’s Life, but I’ll explain why later.
In Ratatouille, we see animals experimenting with their growing personification in small, controlled experiments. Remy wants to cook, something only humans explicitly do. He crafts a relationship with a small group of humans and finds success. Meanwhile, the villain of Ratatouille, Chef Skinner, disappears. What happened to him? What did he do with his newfound knowledge that animals were capable of transcending their instincts and performing duties better than humans?

It’s possible that Charles Muntz, the antagonist of Up, learned of this startling rumor, giving him the idea to begin inventing devices that would harness the thoughts of animals, namely his dogs, through translator collars. Those collars indicated to Muntz that animals are smarter and more like humans than we think. He needed this technology to find the exotic bird he’s obsessed over, and he even comments on how many dogs he’s lost since he arrived in South America.

But then Dug and the rest of his experiments are set free after Muntz’s demise, and we don’t know the full implications of that, but what we do know is that animosity between the animals and humans is growing steadily. Now that humans have discovered the potential of animals, they are beginning to cross the line. To develop this new technology, the humans begin an industrial revolution hinted in at Up.

UPDATE: Some have pointed out that Muntz was working in South America before the events of Ratatouille. This is true, but it is not explicitly stated how and when he developed the collars. Also, we know Ratatouille takes place before Up for several reasons. In Toy Story 3, a postcard on Andy's wall has Carl and Ellie's name and address on it (including their last names to confirm). This confirms that in 2010, the time of Toy Story 3, Ellie is still alive or hasn't been dead long. This supports the idea that Up takes place years later.

In the beginning of Up, Carl is forced to give up his house to a corporation because they are expanding the city. Think on that. What corporation is guilty for polluting the earth and wiping out life in the distant future because of technology overreach?
BNL

Buy-n-Large (BNL), a corporation that runs just about everything by the time we get to Wall-E. In the “History of BNL” commercial from the movie, we’re told that BNL has even taken over the world governments. Did you catch that this one corporation achieved global dominance?
Interestingly, this is the same organization alluded to in Toy Story 3:

In Finding Nemo, we have an entire population of sea creatures uniting to save a fish that was captured by humans. BNL shows up again in this universe via another news article that talks about a beautiful underwater world. In Finding Nemo, lines are being crossed. Humans are beginning to antagonize the increasingly networked and intelligent animals.
Think about Dory from Finding Nemo for a second. She stands apart from most of the other fish. Why? She isn’t as intelligent. Her short-term memory loss is likely a result of her not being as advanced as the other sea creatures, which is a reasonable explanation for how rapidly these creatures are evolving.

It’s likely that the sequel to Finding Nemo, which is about Dory, will touch on this and further explain why. We may also get some more evidence pointing to animosity between humans and animals.
And that is the furthest movie in the “animal” side of things. When it comes to A.I., we start with The Incredibles. Who is the main villain of this movie? You probably thought of Buddy, a.ka. Syndrome, who basically commits genocide on super-powered humans.

Or does he?
Buddy didn’t have any powers. He used technology to enact revenge on Mr. Incredible for not taking him seriously. Seems a little odd that the man went so far as to commit genocide.
And how does he kill all of the supers? He creates the omnidroid, an A.I. “killbot” that learns the moves of every super-human and adapts. The omnidroid eventually turns on Syndrome, which leads us to believe that he was being manipulated by machines the entire time in order to wipe out the biggest threats to robot dominance, super-powered humans. The movie even shows clips of the superheroes with capes being done in by inanimate objects, such as plane turbines…accidentally.

UPDATE: Someone suggested that Randall being sent back in time is what inspired Edna to create Violet's invisibility suit. Also, some have questioned whether or not Syndrome actually was manipulated by his own technology. Keep in mind that the movie strongly suggests it takes place before modern times. The beginning is set in what appears to be the late 60s or early 70s, meaning the events of the movie must be in the late 80s or early 90s. This is a proper setup for Toy Story, as we are starting to see machines questioning their purpose in life. It's possible that Syndrome created this technology to become better than his idol. That doesn't explain his thirst for blood revenge. It seems he became consumed by hatred, and leads me to suggest that the machines wanted him to use them to suit his needs, since they are his slaves after all. It's either that, or the machines knew that killing off the supers was the only thing stopping them from dominating the world via BNL.

But why would machines want to get rid of humans in the first place? We know that animals don’t like humans because they are polluting the Earth and experimenting on them, but why would the machines have an issue?
Enter Toy Story. Here we see humans using and discarding “objects” that are clearly sentient. Yes, the toys love it Uncle Tom style, but over the course of the Toy Story sequels, we see toys becoming fed up.

The toys rise up against Sid in the first movie. Jesse resents her owner, Emily, for abandoning her. Lotso Huggin’ Bear straight up hates humans by the third movie. Toys are obviously not satisfied with the status quo, providing a reason for why machines would eventually be quick to wipe out the strongest humans.
With the super-humans all but gone, mankind is vulnerable. Animals, who want to rise up Planet of the Apes style, have the ability to take over, but we don’t see this happen.
Also, A.I. never takes over humans. Why do you think that is? It’s reasonable to assume that machines did take over, just not as we expected. The machines used BNL, a faceless corporation (which are basically faceless in nature) to dominate the world.
In each of the Toy Story movies, it’s made painfully clear that sentient objects rely on humans for everything. For fulfillment and even energy. It’s hinted at that the toys lose all life when put away in “storage” unless they are in a museum that will get them seen by humans.
So machines decide to control humans by using a corporation that suits their every need, leading to an industrial revolution that eventually leads to…pollution.
When the animals rise up against the humans to stop them from polluting the earth, who will save them? The machines. We know that the machines will win the war, too, because after this war, there are no animals ever to be seen again on Earth. Who’s left?

Because the machines tip everything out of balance, Earth becomes an unfit planet for humans and animals, so the remaining humans are put on Axiom (or Noah’s Ark if you want to carry on the Biblical theme where Wall-E is basically Robot Jesus and his love interest is aptly named Eve) as a last-ditch effort to save the human race.
On Axiom, the humans have no purpose aside from having their needs met by the machines. The machines have made humans dependent on them for everything because that is how they were treated as “toys.” It’s all they know.
Meanwhile on Earth, machines are left behind to populate the world and run things, explaining human landmarks and traditions still being prominent in Cars. There are no animals or humans in this version of Earth because they’re all gone, but we do know that the planet still has many human influences left. In Cars 2, the cars go to Europe and Japan, making it plain that this is all taking place on Earth as we know it.
So what happened to the cars? We’ve learned by now that humans are the source of energy for the machines. That’s why they never got rid of them. In Wall-E, they point out that BNL intended to bring the humans back once the planet was clean again, but they failed. The machines on Earth eventually died out, though we don’t know how.
What we do know is that there is an energy crisis in Cars 2, with oil being the only way society trudges on despite its dangers. We even learn that the Allinol corporation was using “green energy” as a catalyst for a fuel war in order to turn cars away from alternative energy sources.

That “clean” fuel could have been used to wipe out many of the cars, very quickly.

UPDATE: Someone pointed out that "all in all" means the same thing as "by and large" making the connection between Cars and Wall-E even more appealing.

Which brings us back to Wall-E.
Have you ever wondered why Wall-E was the only machine left? We know that the movie begins 800 years after humans have left Earth on Axiom, governed by the AutoPilot (another A.I. reference).
Could it be that Wall-E’s fascination with human culture and friendship with a cockroach is what allowed him to keep finding fulfillment and the ability to maintain his personality? That’s why he was special and liberated the humans. He remembered the times when humans and machines lived in peace, away from all of the pollution caused by both sides.

After Wall-E liberates the humans and they rebuild society back on Earth, what happens then? During the end credits of Wall-E, we see the shoe that contains the last of plant life. It grows into a mighty tree. A tree that strikingly resembles the central tree in A Bug’s Life.
That’s right. The reason no humans exist in A Bug’s Life is because there aren’t a lot left. We know because of the cockroach that some of the insects survived, meaning they would have rebounded a bit faster, though the movie had to be far enough in the timeline for birds to have returned as well.
But there’s more. There’s something strikingly different about A Bug’s Life when compared to other Pixar portrayals of animals. Unlike Ratatouille, Up and Finding Nemo, the bugs have many human activities similar to what the rats in Ratatouille were just experimenting with. The bugs have cities, bars, know what a bloody mary is and even have a travelling circus. This all assumes that the movie is in a different time period.
The other factor that sets A Bug’s Life apart from other Pixar movies is the fact that it is the only one, besides Cars and Cars 2, that doesn’t revolve (or even include) humans.

UPDATE: OK there is a a lot of contention over the idea that A Bug's Life takes place post-apocalypse, but hear me out. The reason I am so inclined to push the idea is because of how different the bug world is from the "animal" movies. No other Pixar movie has animals wearing clothing, wild inventions, animals creating machines or so much human influence like bars and cities. In Finding Nemo, the most human thing we see is a school, and even that is pretty stripped down. But in A Bug's Life, we have a world where humans are barely even implied. At one point, one of the ants tells Flik not to leave the island because there are "snakes, birds and bigger bugs out there." He doesn't even bring up humans. Yes, there are some humans, like the kid who allegedly picked the wings off of the homeless bug, but that still fits in a post Wall-E world. Also, the bugs have to be irradiated for them to live such long lifespans. The average lifespan of an ant is just three months, but these ants all survive an entire summer and allude to being around for quite some time. One of the ants even says he "feels 90 again." That works if you accept that the ants are sturdier due to evolution and mutated genes.

So what happens? Humanity, machines and animals grow in harmony to the point where a new super species is born. Monsters. The monsters civilization is actually Earth in the incredibly distant future.
Where did they come from? It’s possible that the monsters are simply the personified animals mutated after the diseased earth was radiated for 800 years. (Not during Wall-E. I would guess that it took hundreds of years after Wall-E for the animals to become monsters.) The alternative could be that humans and animals had to interbreed to save themselves. Gross, I know, but plausible since the lines between animals and humans are constantly up for debate in Pixar.

Whatever the reason, these monsters seem to all look like horribly mutated animals, only larger and civilized. They have cities and even colleges, as we see in Monsters University.

UPDATE: An issue some have found is that this doesn't properly explain what happened to humans. I haven't settled on a theory I really like yet, but I'm leaning towards the idea that monsters and machines eventually forgot that they need humans and got rid of them again, not realizing their mistake until all humans died out, leading to the necessity for time travel. Another explanation is that humans just couldn't survive on Earth anymore.

In Monsters Inc., they have an energy crisis because they are in a future earth without humans. Humans are the source of energy, but thanks to the machines, again, the monsters find a way to use doors to travel to the human world. Only, it’s not different dimensions.

The monsters are going back in time. They’re harvesting energy to keep from becoming extinct by going back to when humans were most prominent. The peak of civilization, if you will.
Though a lot of time has passed, animosity towards humans never really went away for animals/monsters. Monsters must have relied on anti-human instincts to believe that just touching a human would corrupt their world like it did in the past. So, they scare humans to gather their energy until they realize that laughter (green energy) is more efficient because it is positive in nature.

UPDATE: An alternative explanation that fits even better that some of you brought up: The machines and monsters created the time travel doors but realized that messing with time could erase their existence and change history. So, they falsely trained monsters to believe that humans are toxic and from another dimension, making it suicide for a monster to interact too much with their world.

We even see a connection between A Bug’s Life and Monsters Inc. via the trailer we see in both movies. As you can see, the trailer looks exactly the same, except the one in A Bug’s Life is noticeably older and more decrepit, while the one in Monsters Inc., where Randall is sent via a door, has humans and looks newer.

Look at the picture below. On the left is the trailer from A Bug’s Life and the one on the right is from Monsters Inc.
Trailers

The one on the left looks older and more rundown. Even the vegetation is noticeably dryer and there’s less of it. The trailer on the right has humans and the frame even includes tall grass and a tree hanging overhead.

UPDATE: Some have argued that the trailer in A Bug's Life should be nothing but dust. I disagree based on how barely intact other buildings were in Wall-E. They also bring up the bug zapper that is powered by electricity. The zapper could easily be solar powered, just like Wall-E. The bugs probably used it as a light source to signal other bugs to "Bug City." Also, the trailer in A Bug's Life never shows lights in the trailer like it does for Monsters Inc.

That said, Monsters Inc. is so far the most futuristic Pixar movie. By the end, humans, animals and machines have finally found a way to understand each other and live harmoniously.
And then there’s Boo. What do you think happened to her? She saw everything take place in future earth where “kitty” was able to talk. She became obsessed with finding out what happened to her friend Sully and why animals in her time weren’t quite as smart as the ones she’d seen in the future. She remembers that “doors” are the key to how she found Sully in the first place and becomes…

A WITCH.
Yes, Boo is the witch from Brave. She figures out how to travel in time to find Sully, and goes back to the source: the will-of-the-wisps. They are what started everything, and as a witch, she cultivates this magic in an attempt to find Sully by creating doors going backwards and forwards in time.

UPDATE: Just to clarify: The theory is that Boo discovered a way to use doors to travel through time on her own, possibly by developing magic on her own. She probably went back in time to the Dark Ages to get more magic from the will-o-wisps.

How do we know? In Brave, you can briefly see a drawing in the workshop. It’s Sully.
sully-brave

We even see the Pizza Planet truck carved as a wooden toy in her shop, which makes no sense unless she’s seen one before (and I’m sure she has since that truck is in literally every Pixar movie). If you look closely, you can see the carved truck below.
Brave-Easter-Egg

You remember Merida opening doors and the witch constantly disappearing? It’s because those doors are made the same way from Monsters Inc. They transport across time and that is why Merida couldn’t find the witch.

UPDATE: A lot of people have brought up how easter eggs are scattered throughout all the Pixar movies. I barely scratch the surface, but a great theory offered by some that I support is that these easter eggs are planted by Boo either intentionally or accidentally as she travels through time to find Sully. Some support for that is the fact that every easter egg in Brave lies in her workshop.

Does Boo ever find Sully? I like to think so. He surely reunited with her at least once as a child at the end of Monsters Inc. but eventually he had to stop visiting.
But her love for Sully is, after all, the crux of the entire Pixar universe. The love of different people of different ages and even different species finding ways to live on Earth without destroying it because of a lust for energy.
And that is the Pixar Theory.
Got any ideas of your own about this secret Pixar world? Share them in the comments below.
All images courtesy of Disney/Pixar