To complicate things further, people like Alec Baldwin and Ricky Gervais have appeared as themselves and as in-universe characters. There was also that episode where Homer befriends a guy named Ray, who happens to look and sound exactly like Ray Romano -- and they somehow discuss Everybody Loves Raymond as a series, because even in a cartoon, the most fantastical thing we can imagine Ray Romano doing is talking drolly about himself. The boundary between reality and fiction is as strained as Moe's will to live. There's a reason for this, so bear with me here.

... and evil overlord Matt Groening appears as "the creator of Futurama" at a convention.

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And, going the other way, there is a pile of Bart Simpson dolls on a giant garbage ball ...

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... the sewer mutants cobble together a hot air balloon made out of Macy's Day Parade floats, including pieces of Bart ...

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... and figures and plush toys appear in other episodes.

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Clearly there's a whole lot of paradoxin' going on here. But it gets worse when you realize that, at other times, they even share the same universe. A universe where, it seems, both The Simpsons and Futurama are simultaneously TV shows and not TV shows.

Fry shows up on the couch at one point ...

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... and in one Simpsons episode set in the far-flung future of 2013, Bender appears in a car with Homer and Bart ...

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... And in Futurama, a heart carved into the wall near the entrance to Robot Hell reads "HS + MB" -- who else but Homer Simpson and Marge Bouvier? While Fry's dog, Seymour, is looking for his owner in that episode that made you cry more over a cartoon pet than any of your real ones, he passes a mini-golf course with a suspiciously familiar sign.

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It's well known that Homer and Marge conceived Bart in exactly that location, and they even tried to re-create it later to rekindle their passion. But by far the most extreme example of the two sharing a universe is the crossover episode "Simpsorama."

So how can they understand each other to be fictional and yet exist side by side at the same time? And why the s**t does nobody question why the Simpsons are yellow?

Well, it all leads back to the first time they crossed over. What's that? You didn't know they'd crossed over once before? Jeez, try reading a book sometime.

The "Infinitely Secret Crossover Crisis" is a comic book miniseries that was first published in 2002, and it's a way more interesting story than the episode. The Futurama crew find themselves trapped inside a Simpsons comic, put there by those big floaty brains who previously transported them into book worlds. Once there, they break the heavy news to the Simpsons that they are, in fact, fictional characters. Then, in trying to get home, the crew accidentally destroys the boundary between universes, sending all of Springfield tumbling into the real world, circa 3000.

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In the sequel, the people of New New York do what anyone would do in that situation: They decide that fictional characters aren't people and thus have no rights, and they enslave them. Of course, the "fics" won't stand for this and revolt, releasing every fictional character from every book ever written.

Eventually they patch things up, and the fics are sent back to their books -- all, that is, except the Simpsons. The story kinda wraps up without showing how they get home. Their book is destroyed, so where do they go?

Well, Futurama has time-travel episodes like other sitcoms have mother-in-law-comes-to-stay episodes. So it makes sense that Professor Farnsworth would just send them back to the time their series was set. Back where they kinda-sorta belong and out of his purely metaphorical hair.

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"Good news, everyone! I AM GOD!"

Which then explains how the crossover episode can exist as well as the comic -- in the alternate timeline this creates, the Simpsons are now living in the same world as Futurama, just a thousand years earlier.

There's just one problem: If every fictional character ever created was released, there must have been hundreds of versions of the Simpsons let loose -- one for each issue of the comics, plus whatever other books the characters have appeared in. So where did all these extras go? Back in time, of course, in a big, sweaty, yellow orgy of a paradox.

The show first appeared on TV in 1987, which is old enough for it to have lived, died, and had a hollow, nostalgia-fueled reboot by now. By that timeline, Bart would have been born in 1977. Next year he'll be due for a mid-life crisis and a depressing 40th birthday bash at Moe's. Even Maggie is pushing f*****g 30 by now.

We know what the Simpsons actually looked like in the '80s. It wasn't this ...

But since he's still 10 in the current season, Bart must have been born circa 2006. He's younger than YouTube. In fact, if we assume that each episode is set in the year it was released (and they often tell us exactly that), then some version of Bart had to have been born every single year between 1977 and 2006. There is a "REALLY Into The Smashing Pumpkins" era Bart and a "First Made Out With A Girl In A Movie Theater Playing Pulp Fiction" era Bart.

We've even seen a couple of these different Bart births. The classic episode "I Married Marge" tells of Bart's conception and birth in 1980. The Season 19 episode "That '90s Show" retconned it to happen sometime around 1998. And Season 26's "The Kids Are All Fight" flashes back to 2009, when Bart was 4 and Lisa was 2. You might also recognize 2010 as the year Lisa gets married. So both a 3-year-old and a 23-year-old Lisa exist simultaneously -- and, hell, there's a standard 8-year-old version running around too, since Seasons 21 and 22 aired that year.

It's a bigger mess than Terminator Genisys. But it's not just time that's been fucked: Space is full of gloryholes too.

Over the Simpsons' back fence is usually just another house, but we've also seen a forest, a graveyard, and the Power Plant's parking lot there. In one episode, Homer is proud that he walks all the way to Moe's, before the camera zooms out to reveal it's only two doors down from home. In the movie, Moe's is shown to be right next door to the church, for the purpose of a single gag.

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And in this world it's called Moe's Bar instead of Moe's Tavern.

But it looks like everything jumps around because we're not seeing one city here. In any given episode, we could be looking into any of those parallel Springfields -- each one populated with a different version of the Simpsons and co. Many of which die horribly.

In fact, we see the main cast horribly killed right in front of us all the time -- we just choose to ignore it because they're framed as parts of Halloween specials. Homer is mauled by a werewolf Flanders. The whole family is turned inside-out by fog. Groundskeeper Willie murders school kids from beyond the grave. Snake Jailbird's sentient hair kills Apu and Moe. The entire city is wiped out by a nuke. And Y2K. And zombies. And dolphins.

But hey, next week we'll just scoot over to the next Springfield, the one that wasn't destroyed by giant advertising mascots, and pretend nothing happened. The "Treehouse Of Horror" specials aren't the "What if?" scenarios we've always assumed; they're the universe trying to repair its mistakes. They're particularly gruesome errors in the space-time continuum, like an annual stroll through the room full of failed Ripley clones.

And with the barriers between reality and fiction weakened, the parody episodes take on a new meaning. Maybe "The Shinning" isn't a parody of The Shining but a freak accident where one incarnation of the characters just falls into the original novel.

Hell, even the opening couch gags show some weird alternate realities, where the family are sea monkeys, or squashed by a Monty Python foot, or (shudder) animated by Robot Chicken.

The Simpsons have been made of LEGO. They've been characters in the Bible. There are so many versions of reality and so many different Springfields that we can never know which one we're looking into. One's set in the real world in 2004, where Matt Groening signs Milhouse's Bender doll at a convention. Another takes place in 1997, where fictional characters Mulder and Scully investigate Homer's alien sighting. The rules of reality change on an episode-by-episode basis. Hell, it could change on a minute-by-minute basis; who knows? That might explain the haphazardly terrible nature of the last 15-odd years of The Simpsons.

And if the most recent Halloween episode is anything to go by, the very fabric of space-time is stressed beyond its limits and about to implode.

So if you feel like the series is getting stale, just start from the beginning with this theory in mind. It changes the whole show. Suddenly, you have over 600 fresh episodes of The Simpsons. You're welcome.

Michael Irving is more fluent in Simpsons quotes than in English, although he only speaks enough Season 10+ to ask where the bathroom is. He practices on Twitter at @MikeIrvo.

See why you should give Arnie Pye some love in The 5 Most Underrated 'Simpsons' Characters, and learn how The Simpsons predicted everything in 5 Absurd (But Mind-Blowing) Pop Culture Conspiracy Theories.

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