WARNING: The following contains spoilers for What If...? Season 1, Episode 5, "What If… Zombies?!" streaming now on Disney+.
It's safe to say that the "Thanus theory" is one of the weirdest pieces of fiction fans have ever concocted, not just for the Marvel Cinematic Universe, but movies in general. It began circulating after the release of Avengers: Infinity War, as folks on Reddit posited the Mad Titan could be stopped if Ant-Man shrunk, crawled into Thanos through his backside and expanded in size to kill the villain. Thankfully, that never came to pass, but the idea does get remixed in "What If... Zombies?!" thanks to a brutal kill that leads to a very tragic ending.
It's such a ridiculous notion even the Russo brothers wondered how the heck someone could come up with that as a strategy to stop Thanos. That said, the MCU actors weren't sore about the theory and actually had fun with it, with Josh Brolin poking fun at it on social media.
However, this alternate reality where the undead have overtaken the world does lean into the idea of a pint-sized hero crawling into a villain's orifice to save the day. It happens as the last remnants of Earth's Mightiest Heroes hop a train to get to New Jersey to possibly find a cure for the zombie apocalypse.
At the heart of it is Hope Van Dyne (aka the Wasp), who's helping lead the heroes along with Okoye. As the train hustles off, it gets dark for Sharon Carter, now wielding Iron Man's gauntlet after Happy Hogan's death. Sadly, Captain America has made his way on the train, mauling Sharon and transforming her from Agent 13 to a zombie. Bucky intervenes and goes after Steve, cutting him in half and taking the shield, however, Sharon's on the warpath and quite hungry.
This all culminates in Hope flying into Sharon's mouth as she hisses, and while it seems at first like she's been eaten, it's all a secret ploy by Hope. When Sharon trains her eyes on Bucky, the Wasp shows no mercy and returns to her usual size, causing Sharon to explode in a gory scene, with guts and blood splattered everywhere in the car.
"Uhh, guys, I'm covered in Sharon!" Hope remarks, to which an onrushing Okoye quips, "The kid has hand sanitizer," looking over to Spider-Man. Sadly, the humor's quickly undercut, as Bruce Banner tells her she's in "trouble," pointing to her suit being cut open. We see a flesh wound exposed, which means Hope's been infected after her heroics.
This leads to Hope getting sick, and while Spidey's adamant they'll find a cure for her at their destination, with zombies in the way, Hope has no choice but to sacrifice herself to ensure her peers get to the military base. She turns from the Wasp to Giant Woman, toting the heroes to study the plague, all while zombies scale her and start attacking. However, as she tosses them over the fence and preps for her death, she tells Pete to smile and be optimistic things will work out.
What If...? releases new episodes every Wednesday on Disney+.