At the time, fans didn't know which part of the film Marvel Studios was reshooting or the extent.
But now that the threequel is in theaters, it's clear that Marvel Studios reshot the threequel's bookended conclusion a mere month away from the film's premiere and its theatrical debut.
So how was Quantumania supposed to end and how is it different than what's playing in theaters?
How Ant-Man 3 Originally Ended
In October 2022, a full summary of Ant-Man and The Wasp: Quantumania's plot surfaced online.
With the film now in theaters, the details shared have proven to be accurate with the exception of the threequel's conclusion, which fans now know was refilmed in early January.
The following is a breakdown of what Marvel Studios changed during Quantumania's midnight-hour reshoots.
Warning - the rest of this article contains spoilers for Ant-Man and the Wasp: Quantumania.
Kang Escapes, Scott & Hope Are Trapped
Instead of Kang the Conqueror's confusing fate where he's seemingly shrunk down into a Multiversal engine core, Kang was supposed to survive.
According to the plot leak, Kang stops Scott from escaping to his universe along with the rest of his family and beats him to a pulp, just as he does in the final film.
But when Hope returns to save Scott, they almost trap Kang in the Quantum Realm; however, he manages to escape, trapping the two there instead.
Just like in the final cut, Hank, Janet, and Cassie escape back to San Francisco.
But since Scott and Hope are trapped, Hank guarantees his wife and granddaughter that they will find them.
This, of course, is drastically different from Hank and Janet attending Cassie's un-birthday party and eating bad birthday cake from Baskin Robbins.
Back in the Quantum Realm, Hope and Scott look out over the subatomic landscape as Hope tells Scott that their family will be okay and that they have to trust them to find them both. She also says that Cassie will know what to do.
Sometime later, Cassie is shown running all kinds of programs on different computers. As she stares at the screen, she sees something, causing her eyes to go wide and she gasps. Then, in true WandaVision fashion, the scene cuts to black.
Why Marvel Saved Ant-Man From the Quantum Realm
Marvel Studios has a reputation for tweaking and retooling films up until the last minute. However, completely overhauling a film's ending weeks before its premiere is just shocking. It's even more so given that many of the last-minute changes are actually some of the audiences' biggest complaints.
Not only did fans not like the idea of Kang losing to Ant-Man, but they also didn't like how Cassie oh-so conveniently reopened the portal, allowing Scott and Hope to return.
In fact, many felt that someone in the Ant-Man family should die or remain trapped in the Quantum Realm, which is exactly what the writers initially penned.
The original ending was also better for Cassie's character as it laid the groundwork for her own upcoming hero story.
So the obvious question here is why? Why did Marvel Studios give Kang a different fate and why didn't the studio want Scott and Hope trapped in the Quantum Realm?
One of the possibilities is to avoid repetition. Ant-Man and The Wasp's post-credits scene ended with Scott Lang trapped in the Quantum Realm, only for him to make a triumphant return in a future Avengers film to save the day. Sound familiar? Marvel Studios may have realized this similarity to the original idea for Quantumania's ending and decided a change was for the best.
There are, of course, other potential reasons. Was the reverse the result of a change to the greater MCU Multiverse Saga story? Hopefully, future films or Loki Season 2 will be able to answer that question.
But for now, it seems that, just like Scott and Kang, Ant-Man 3 really needed more time.
Ant-Man and The Wasp: Quantumania is playing in theaters worldwide.