One of the more popular fan theories that circulated online prior to the release of Avengers: Endgame was a possible strategy for Ant-Man to insert himself into Thanos via the villain's anus and suddenly expand, bursting the Mad Titan from the inside out. This was, of course, dubbed the "Thanus Theory."
According to Endgame co-writer Stephen Markus, however, Thanos' superhuman endurance, as established in Avengers: Infinity War, would never give way to Ant-Man should he try to grow within the titanic walls of Thanos' rectum.
"Thanos could take a punch from the Hulk, we've seen that. And it stands to reason his whole body is at least as strong as that,” observed Markus in an interview with Empire. "If Ant-Man expanded, he would be simply crushed against the immovable walls of Thanos’ mighty rectum."
The Thanus Theory has received a fair amount of good-natured criticism from Marvel Studios' stars since surfacing online. Paul Rudd wondered why Ant-Man would choose the anus, of all possible points of entry, while co-director Anthony Russo noted that theory was "the most ridiculous" he and co-director Joe Russo had heard.
Directed by Joe and Anthony Russo, Avengers: Endgame stars Robert Downey Jr. as Iron Man, Chris Evans as Captain America, Mark Ruffalo as Bruce Banner, Chris Hemsworth as Thor, Scarlett Johansson as Black Widow, Jeremy Renner as Hawkeye, Brie Larson as Captain Marvel, Paul Rudd as Ant-Man, Don Cheadle as War Machine, Karen Gillan as Nebula, Danai Gurira as Okoye and Bradley Cooper as Rocket, with Gwyneth Paltrow Pepper Potts, Jon Favreau as Happy Hogan, Benedict Wong as Wong, Tessa Thompson as Valkyrie and Josh Brolin as Thanos. The film is in theaters now.