Avengers: Endgame will reportedly spend a full three hours on the climactic battle between the Avengers and Thanos, the unstoppable force that turned great swaths of Earth’s population into dust at the end of 2018’s Infinity War. But while Marvel Entertainment continues to build buzz and uncertainty around the highly anticipated end of a saga told by more than a decade’s worth of superhero movies, some fans already have a theory as to what’s going to go down. It’s a theory that has gained so much traction online that even the movie’s directors — and the man behind Thanos himself — have joined in.

I’ll toss out a spoiler warning, just in case this theory turns out to be true. Because what we are about to discuss is so stupid, so implausible, it almost makes sense:

Ant-Man will defeat Thanos by crawling up the Mad Titan’s butt and expanding inside of him.

Yes, the idea of an Avenger killing off the ultimate enemy by climbing into his butt is a goofy fan theory, and a gross one at that. But that hasn’t stopped fans from standing by it for nearly two years now. What was once a Reddit joke has become a widespread meme, and some Marvel fans are arguing that, hey, maybe this potential plot turn is actually a great idea. And there may even be a real chance for Ant-Man to destroy Thanos from within, as wild as that sounds — because there’s legitimate comic book precedent for the tactic.

You can thank (or blame) Reddit for this theory

According to Know Your Meme, the origins of this radical theory about Endgame’s true, well, end game date back to before Avengers: Infinity War was released. Perhaps a bold assertion to some, the Thanus Theory (as I’ll conveniently dub it for now) actually has years of support behind it, in one form or another.

Ant-Man (played by Paul Rudd) isn’t an especially prominent Avenger, with only two solo films to his name; he also was absent from Infinity War, the most visible Marvel playground thus far.

But the quippy hero also known as Scott Lang remains a force to be reckoned with, as made especially clear in 2016’s Captain America: Civil War, which set the stage for Infinity War. Where 2015’s Ant-Man focused on establishing the origins of snarky criminal Lang and his growth into his superhero role, Civil War gave the character and his size-changing skills a great showcase. In Civil War, his suit has been upgraded to be much more powerful, allowing him to do much more than shrink to insect-size, as seen in his own movie. The movie reveals that Ant-Man can actually grow 60 feet tall too, into a super-strong hero appropriately called Giant Man.

And the Giant Man reveal is a key element of the Thanus Theory, because Ant-Man’s ability to shrink and expand is exactly how fans think he can help the Avengers win the final battle against Thanos.

In July 2017, when Marvel fans knew little about Infinity War beyond its promise of an Avengers-Thanos showdown, Reddit users began to brainstorm some of the “worst ways to they can stop Thanos.” Maybe Thanos would die on his own of natural causes. Maybe the whole ordeal would turn out to be Tony Stark’s dream.

Or maybe the Hulk would borrow Ant-Man’s suit, shrink down, crawl into Thanos’s mouth, and journey into his digestive system, before taking him down from within in especially gross and graphic fashion, as posited by Reddit user sodabased:

As soon as the Hulk makes it to the urethra he turns his suit off. Thanos’s manhood explodes as a blood-covered Hulk emerges from the bloody mess. Thanos falls down unconscious and slowly bleeds to death. The camera tightens on Spiderman who looks at Doctor Strange, “Well let that be a lesson for ya Doc! Hulk smash Kidney Stones!” The camera then pans to each and every one of the heroes who have survived the war as they do a good guffaw.

Sodabased’s theory became the top-rated reply in the thread, and hailed as not the worst way to kill the unstoppable Thanos, but the best. But why let Hulk take care of business, some fans wondered, suggesting that Ant-Man could, and should, do it himself.

This idea was reinforced when another Reddit user made a corresponding poster and uploaded it to the Marvel subreddit in December 2017, albeit one that suggested a much less obscene process than sodabased’s. Tiny Ant-Man could crawl into Thanos’s ear and simply destroy him from inside his head. The poster begat less conversation, but it still received a lot of attention, earning more than 1,200 upvotes.

After that, however, fans by began prepping for Infinity War with more legitimate speculation as 2018 rolled around. Things were quiet for a while on the Thanus Theory front — but that changed when Infinity War finally arrived.

Maybe Ant-Man skipped Infinity War to prep for his big finale

Cut to April 2018. Infinity War is out. A lot of our superhero friends have been turned to dust by Thanos’s Infinity Gauntlet. Audiences, who show up to see the film in droves, are left to speculate which heroes are truly dead, how some of them might return, and whether any of the original Avengers will survive the next movie.

But one Avenger who does not appear in Infinity War whatsoever is Ant-Man.

His absence is notable, but it’s not explained during Infinity War. In fact, Marvel didn’t reveal Ant-Man’s whereabouts until July 2018, when one of Ant-Man and the Wasp’s end credits scenes showed that he’s trapped inside the quantum realm — alive, thankfully, but currently unable to participate in all the world-saving business the rest of the Avengers are up to.

So in the period between Infinity War’s release and that of the Ant-Man sequel, fans are forced to draw their own conclusions. It’s at this point that Twitter user Filmgloss finds viral fame by dredging up memories of that old Thanus Theory Reddit post from 2017:

marvel saw the post about how ant man could defeat thanos by crawling into his ass and instantly growing in size and that’s why they didn’t put him in the movie, send tweet — c a t (@filmgloss) April 30, 2018

Filmgloss’s tweet was popular on Twitter, garnering more than 11,000 retweets and 30,000 likes. But it gained even more traction on Tumblr, where a screencap of the tweet now has more than 83,000 notes and counting. From there, it even made its way to Paul Rudd himself, when a journalist asked him about it during the Ant-Man and the Wasp press tour.

so paul rudd read my tweet about ant man crawling into thanos’ ass and expanding OUT LOUD in an INTERVIEW and discussed it i’m in shock pic.twitter.com/YfBsPMnfoW — c a t (@filmgloss) July 21, 2018

Rudd expressed his doubts that such a plan would work, though he didn’t veto it outright. Ant-Man and the Wasp came and went, and once again, online discussion of the Thanus Theory died down — until now, as Marvel fans on Tumblr, Twitter, Facebook, and, naturally, Reddit, have once again raised the idea in the lead-up to Endgame.

It helps that Ant-Man has appeared in a handful of Endgame trailers over the past few months, thus confirming that he’ll appear in the final Avengers film. And one of those trailers even suggests that he may hold the answer to fighting back against Thanos’s seemingly unstoppable finger snap.

But Know Your Meme attributes the latest resurgence of the Thanus Theory to a much more recent Reddit discussion, which saw a comment in a new Endgame trailer thread garner more than 15,000 upvotes.

“Are we still betting on Ant-Man defeating Thanos by crawling up his butt then expanding?” asked a user named Aimless Devastator on March 14, after the movie’s most recent trailer premiered.

For many Marvel fans on Tumblr and Twitter, the answer seems to be an unwavering yes. And as a result, ahead of Endgame’s April release, the Thanus Theory has achieved major meme status, with years of build-up behind it:

ant-man will defeat Thanos by crawling up his butt and expanding pic.twitter.com/MfPcxgwb0J — ray sipe (@raysipe) March 24, 2019

literally almost every mcu fan: haha what if Nick Fury's eye was scratched out by the cat



Captain Marvel: Nick Fury's eye was scratched out by the cat



literally almost every mcu fan: haha what if ant-man went into thanos's ass then grew to defeat him



Avengers Endgame: — Jennifer (@sapphic_tracer) March 25, 2019

ant-man when he changes size in thanos’ ass https://t.co/TkHM1EgfyF — Eddy Burback (@eddyburback) March 23, 2019

Importantly, the Thanus Theory appears to have the support of three influential members of the MCU: Josh Brolin, who plays Thanos, and the Russo brothers, who directed both Infinity War and Endgame.

Brolin uploaded a video to Instagram of him preparing to “#flushantman”:

And the Russo brothers changed their Instagram profile picture with a version of the meme:

Why this theory may not be as ridiculous as it sounds

Marvel fans who subscribe to the Thanus Theory aren’t backing down, continuing to spread the meme on social media. And on some level their hearts are in the right place: It would be nice to give Ant-Man a big moment in Endgame, even if said moment could easily be taken to some inappropriate, offensive places by certain fans. It’s not like Marvel movies haven’t indulged in some ridiculous humor once in a while.

But regardless of whether people are caught up in the juvenile humor of the Thanus Theory, there’s actually some serious canonical credence to it. Jokesters on Reddit aren’t the first to think of the tactic of literally taking Thanos down from within. Marvel has considered it too — via a character only recently introduced to the Marvel Cinematic Universe: Monica Rambeau, the daughter of Carol Danvers’s best friend and, in the comic books, a former Captain Marvel herself.

As Vox’s Alex Abad-Santos previously noted:

“During [writer Al] Ewing’s run on The Ultimates (2015), a series about a band of superheroes (including Monica and Carol) who are dealing with cosmic threats, Monica manipulates her energy form to actually enter Thanos’s brain to try to kill the Mad Titan,” as seen in the following frame:

Note that Monica failed to actually kill off Thanos this way; though she managed to make it into his head and hurt him, Thanos ultimately regained control of his brain and forced her out of it. But the attempt does provide an important precedent. And one could reasonably argue, silly though it may sound, that Thanos has more finely tuned control over his brain than he does of his bowels and colon. Perhaps there really is an, uh, opening for Ant-Man to exploit.

But even if Ant-Man doesn’t ultimately destroy Thanos by shrinking down, climbing inside of him, and then growing to be 60-plus feet tall, he could certainly make an honest effort. Better that Ant-Man get the kill over a different forgotten Avenger: Hawkeye.

Avengers: Endgame comes out in theaters April 26.