Warning: This article contains spoilers for What If...? episode 5.

Marvel's What If...? introduced zombies to the Marvel Cinematic Universe, and it secretly reveals Spider-Man's true power. What If...? episode 5 brought zombies to the MCU. After a zombie virus escapes from the Quantum Realm, the undead quickly overrun everything, and the Avengers make things worse. Unfortunately, the zombified Avengers retain their superpowers, so humankind doesn't have much chance after the heroes get infected. Still, there is some hope. In the episode, the remaining heroes, including T'Challa (Chadwick Boseman), Spider-Man (voiced by Hudson Thames), and Ant-Man's (Paul Rudd) head, fly to Wakanda to distribute a zombie cure.

Spider-Man (Tom Holland) first made his MCU debut in Captain America: Civil War. After being recruited by Iron Man (Robert Downey Jr.), Spidey swings onto the scene of a battle against Captain America (Chris Evans) and is an immediate delight. Spider-Man appears in four more movies after Civil War—two Spider-Man films and two Avengers films—each adding different layers to his character. By the time he reaches Spider-Man: Far From Home, the character has become an MCU staple. Though he started as a sidekick to Iron Man in Civil War, Spider-Man is now one of the main heroes bringing the MCU into the future.

Related: Why Bucky Could Let Captain America Die (But Cap Couldn’t Give Him Up)

In What If...? episode 5, Marvel shows Spidey's true powers. Despite a zombie apocalypse ripping the MCU apart during the episode, Spider-Man looks on the bright side. He makes a humorous zombie survival video to show people the ropes of the apocalypse. He also tries to cheer up Hope Van Dyne (Evangeline Lilly) when she knows she's dying of a zombie infection. "Oh, kid. How do you do it?" Hope asks him, wondering how he stays so upbeat. "Practice, I guess," Peter Parker says, listing all the people he's lost. He then remembers a quote from his Aunt May (Marisa Tomei) to always keep smiling when others can't. And with that, the MCU reveals one of Spider-Mans best powers.

Spider-Man pulling his webs in Marvel's What If...?

Spider-Man's ability to remain upbeat is by far his strongest superpower. In the MCU, Peter Parker has been through a lot, and What If...? episode 5 makes it even worse. As of the episode, he's lost Iron Man, the MCU's mysterious Uncle Ben, Aunt May, Happy Hogan (Jon Favreau), and his parents. So he doesn't have a lot of people left. However, despite that, he tries to cheer others up in the face of the apocalypse. His everlasting optimism and his unwavering heart are what make him such a great friendly, neighborhood Spider-Man.

Spidey's heart allows him to use his other powers to the best of his ability. Obviously, Spider-Man's superpowers come in handy when he's taking on villains. After all, optimism isn't why Peter Parker can climb on the ceiling. However, Spider-Man uses his powers heroically because of his heart. At the end of Spider-Man: Homecoming, he runs into a fire and uses his strength to save Vulture (Michael Keaton), despite the villain nearly killing him. Yes, his abilities make him a formidable opponent in a fight, but it's his heart that makes him a superhero.

More: Infinity War: What Would Zombie Thanos’ Snap Do?

Marvel's What If...? releases new episodes Wednesdays on Disney+.

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