WARNING: The following contains spoilers for What If...? Season 1, Episode 5, "What If… Zombies?!" streaming now on Disney+.
This week's episode of What If...? brings to life a classic Marvel story revolving around superheroes joining the ranks of the undead as zombies. In the episode, a journey to the Quantum Realm causes Hank Pym to be exposed to a virus that turns him into a flesh-eating zombie. Unfortunately, his infection eventually spreads to the larger world, and in a matter of weeks, the Earth has succumbed to the virus. While this happens in an alternate universe, Ant-Man and the Wasp: Quantumania opens the terrifying possibility for a similar zombie virus to infect the Marvel Cinematic Universe.
The Quantum Realm is a place of infinite possibility. In the main timeline, Hank finds his long-lost wife there decades after she initially entered it. As a side effect of her exposure to the realm, she obtained strange powers that cured Ghost's cellular destabilization. However, in What If...?, she contracts the quantum virus that later infects Hank and the rest of the world. The virus' origins are unknown, but it affects a person's brain and causes their body to instantly decay following infection. Its transmission is also similar to how it spread in the comics.
In Marvel Zombies, an extradimensional superhero crashes to Earth and spreads an infection known as "the hunger." In this reality, the hunger is insatiable, and those infected can still retain their personality and awareness. Conversely, those infected in What If...? don't retain their consciousness, but they can still use their powers creatively to feed. While the quantum virus is only shown in What If...?, the show's concept of parallel worlds with only slight differences means that there are still risks that could arise in Quantumania.
While unlikely to happen, should a zombie plague infect the main timeline during the events of the next Ant-Man film, the further repercussions across the MCU could be disastrous. Not only does the film continue the adventures of Scott Lang and Hope Van Dyne, but it also introduces Jonathan Majors as Kang the Conqueror. If a zombie plague were to spread at this point in the time stream, the main timeline being infected could be the best-case scenario. Since Kang is a conqueror, he could see the potential in the quantum virus and use it to take over other timelines. Alternatively, he could become infected himself and go on to infect the larger multiverse.
It's also important to note that there is a heavy focus on the Ant-Man family during this What If...? episode. Hank and Janet are briefly present, but Scott Lang and Hope Van Dyne also have their own focuses that push the story forward. The logical reason for this is that the Pyms are the ones that kickstarted the zombie plague. However, since nothing is accidental in the MCU, this could also tease a potentially terrifying zombie encounter for Scott and Hope in Quantumania.
With Kang being included in the next Ant-Man film, the stakes were already feeling much higher. But with the potential threat of a quantum virus existing in the realm, there's a new sense of tension that will stick with the fans. While it's unlikely the plague will infect the main MCU timeline, there are still other dangers in the Quantum Realm. As a result, Scott Lang and Hope Van Dyne will have to be even more careful in Quantumania.
To see what other horrors the multiverse holds, What If...? releases new episodes every Wednesday on Disney+.