Acting for Two: Jonathan Majors portrays Kang the Conqueror throughout most of this movie's runtime, and later portrays a countless number of his variants in the mid-credit scene, including Immortus, Scarlet Centurion and Rama-Tut. He also portrays Victor Timely in The Stinger.
Kathryn Newton admitted that there were days where she didn't always know what scenes she was shooting for this film. Notably, she was unaware that M.O.D.O.K was chasing her during one scene in the climax.
Owen Wilson noted in an interview that he wasn't aware that Mobius and Loki were going to appear in The Stinger for this film, believing it was only part of the Loki show and nothing else.
Hope's shorter hairstyle and darker color in this movie was Evangeline Lilly's doing, as she wanted to pay tribute to Janet Van Dyne's original pixie-style haircut in the comics.
David Dastmalchian came up with much of Veb's movements during the character's mocap process, and also invoked budding chemistry between Scott and Cassie that wasn't in the original script.
Bill Murray was interested in joining Marvel for a while, and even phoned Kathryn Newton to ask if she was okay with him joining the cast of this film. Working with Peyton Reed was also a motivating factor for Murray.
Jonathan Majors jumped at the opportunity to portray Kang in this film, as he really wanted to play a supervillain after many projects in his film career where he was merely a normal person.
Kathryn Newton considered joining the franchise a "dream come true", and was eager to work with Paul Rudd.
According to Peyton Reed, Corey Stoll agreed to reprise the role of Darren Cross both to work with the Ant-Man crew again and because, as a comics nerd, he knew who M.O.D.O.K. was and loved the idea of getting to play him. Stoll himself noted that he really had fun working on Cross and Cassie's relationship, noting that he loved the idea of Cassie fighting the man who traumatized her as a child, but still having enough grace to encourage him to be a better person.
The movie's writer Jeff Loveness stated on Twitter that he had always wanted to write a "tortured, classical supervillain burdened with a crusade against fate" for all his career, and was very grateful that he got to do so here.
After being disappointed that Kurt would be written out of this film, David Dastmalchian was more than excited to come back and play Veb instead. He came to really enjoy the mocap process of portraying him, as it was something he had never done before in his film career.
William Jackson Harper admitted that he was a huge geek for the MCU and always wanted to be part of it, meaning he was quick to sign on when the role of Quaz was offered to him.
Katy O'Brian mentioned that after having primarily being villainous henchmen and side characters in her career, she was happy to get to play Jentorra, a heroic leader that expresses more emotion than her previous roles.
Creator Backlash: Minor example, but Jeff Loveness admitted in an interview that he was disappointed in himself for having to cut a scene where Hope would see a version of herself with a son during the probability storm, particularly regarding how the child actor's scenes all ended up being cut as a result.
Dawson Casting: Cassie Lang is in her late teens in this film and is played by the then-24 year old Kathryn Newton.
Defictionalization: Part of the film involves Scott Lang promoting his memoir, Look Out for the Little Guy. Disney released a real life version of this memoir on September 5, 2023.
Dyeing for Your Art: Kathryn Newton, a natural blonde, dyes her hair brunette as Cassie. Evangeline Lily also dyed her hair darker and cut it short to pay homage to Janet Van Dyne's/Wasp's original look
Enforced Method Acting: The coffee barista calling Scott Spider-Man instead of Ant-Man wasn't scripted; the actor playing him legitimately got the two heroes mixed up when saying his line. As such, the reactions of the various guests and Scott himself were all improvised in the moment.
According to MCU: The Reign of Marvel Studios, Victoria Alonso's relationship with Marvel strained during the making of this movie. She had a falling out with Kevin Feige, after she spoke out against Disney at the time. This infuriated Feige, as she broke his cardinal rule of not speaking out against the company. Feige reportedly didn't defend her when Disney fired Alonso from her job at Marvel, which occured just one month after the film's release.
Alonso departure was also allegedly based on her refusal to censor out a Pride sign in the movie for Kuwait's theatrical release. Despite Alonso's refusal, the studios allegedly went against her wishes and still censored the scene.
Curiously enough, the same character's voice actress gets replaced in the Japanese dub, as Rie Takahashi voice her, replacing Rikako Ohta from the same film.
The same goes in the Latin American Spanish dub; in that case, however, the shift was needed because Cassie's previous voice actress, Andrea Arruti, died in 2020, being replaced in this film with Regina Carrillo.
Refitted for Sequel: There were plans for Scott to use giant ants to help fight against Thanos's forces in Avengers: Endgame, but they never made it past the concept art stage. Here, an army of advanced giant ants are used to fight against Kang, albeit under Hank's control instead of Scott's.
Release Date Change: Its first confirmed release date was February 17, 2023. Then, in October 2021, it was pushed back to July 28 of that year, only for it to return to the original February slot due to production of The Marvels taking longer than usual.
Role Reprise: Corey Stoll reprises his role as Darren Cross, a character he hasn't played since the first Ant-Man movie. In a bit of a twist though, his supervillain identity is now M.O.D.O.K rather than Yellowjacket.
Throw It In!: Ruben Rabasa, who played the elderly coffee barista who says, "Thank you, Spider-Man!" admitted the line was just a mix-up for him, and when he said it, he didn't understand why everyone was suddenly laughing.
Wag the Director: The scene where Darren Cross's deformed ass is shown before he's reconstructed into M.O.D.O.K was almost cut from the film, but Corey Stoll asked the producers to keep it because he found it hysterical.
According to Variety, Jonathan Majors nearly missed out on joining the MCU (let alone getting considered for Kang) because he walked out of his first general meeting with Marvel (after having been kept waiting due to busy executives). Luckily, Casting Director Sarah Finn caught up with Majors before he left the building and the rest is history.
According to Peyton Reed, M.O.D.O.K. almost wasn't in the film. Marvel Studios had been wanting to introduce the villain into the MCU for a while. He was considered for previous projects, but the introduction kept getting postponed. Reed only secured the character for this film after realizing they could use him (or rather Darren Cross as M.O.D.O.K.) for explaining in-universe how Kang already knew of the Pyms/Langs.
Early concept art shows that M.O.D.O.K was initially much more heavily armored and screwed up, which would've been the result of him having to adapt to the Quantum Realm himself without Kang to help him.
During the probability storm, Hope was going to see a variant of herself with a son in an early draft in the movie, and there were even scenes shot with a child actor named Lucas Grant in the role. He ultimately was removed from the film due to the storyline changing, making the scene too disjointed to properly incorporate it into the film. This also had the side effect of having Grant's role being removed from the final film.
Hank was planned to wear his original Ant-Man suit when summoning the ants to attack Kang, which would made the Conqueror realize that he's the first person to don the mantle. According to Alex Perez, it was scrapped because it wouldn't have made sense for Hank to have the suit in the Quantum Realm since it wasn't made of nanotech like Scott, Hope and Cassie's, and he wouldn't have time to take it with him when getting sucked into the Quantum Realm.
Additionally, there was an early draft of the film where Hank would've actually died during the story, but have his consciousness take control over the ants stuck in the Quantum Realm, making them a literal Hive Mind under his control. While it's not entirely clear why this was scrapped, Loveness did mention that he didn't want any major deaths in this film to avoid replicating "the Thanos approach".
David Dastmalchian wasn't originally planned to come back for the third Ant-Man film, as Peyton Reed had written out Kurt and the rest of the Wombats due to their lack of relevance within the Quantum Realm plot. However, after the character of Veb was created, Reed realized that David would be perfect for the role, and so phoned him to ask him to portray the character, which he graciously accepted.
Jeff Loveness originally had a Creator Cameo as a henchman of M.O.D.O.K's, being killed by him for speaking out of turn. It didn't make the final cut.
Loveness also wrote a backstory for Kang that was going to be featured in this film, but decided to save it for The Kang Dynasty instead.
Janet was originally planned to utilize more of her "quantum healing" powers that she alluded to in the second film, which would've extended to her having similar phasing powers that Ghost had in that movie. She would've used said abilities to fight Kang in the Quantum Realm and would've tied into her trauma that she carries throughout the film. According to Jeff Loveness, they were removed from the final product because it confused test audiences too much.
At some point, Loveness wanted to include a large, mutated man-sized ant voiced by Werner Herzog that would've spoken to Scott in the probability storm.
Scott was supposed to be significantly more bloody during the climactic fight against Kang, but Disney executives requested to tone it down.
Concept art shows Kang was going to have other abilities at his disposal, including summoning ghostly duplicates to confuse and attack his enemies.
According to Katy O'Brian, Krylar was meant to have a much bigger role in the film than in the end product. Rather than being subjected to Uncertain Doom, Krylar was supposed to have participated in a vehicle chase with Janet and her family within the Quantum Realm, which would've culminated in him somehow getting thrown in jail by Kang. Jentorra would have busted Krylar out during the jailbreak scene, with him trying to convince her that he was still on the side of good, but failing. It was scrapped because it would've caused the film to clock in at 3 hours.
At one point the film was delayed to July 28, 2023, with The Marvels taking its February slot, had this stuck, Ant-Man and the Wasp: Quantumania would've been the third film of Phase 5 instead of being the first installment.
According to Peyton Reed, Darren Cross returning as M.O.D.O.K. for this film was a serendipitous "Eureka!" Moment for the writers. Reed and company were trying to figure out how to bring the Pyms and Langs into the Quantum Realm and how Kang could possibly know about the Ant Family. It then dawned on Reed that they'd already unwittingly introduced a potential 'inside man' back in the first Ant-Man: Darren. Reed realized they could use Yellowjacket's implied fate from that film's climax as the mechanism to bring the Ant Family to the Quantum Realm and explain Kang's familiarity with them.
Peyton Reed said on the Empire Spoiler Specials podcast that Janet met Kang around 21-22 years after Janet was stranded in the Quantum Realm.
Word of Saint Paul: Katy O'Brian suggested that after the Pym-van Dyne family left the Quantum Realm, Jentorra and the rest of the freedom fighters worked with the giant ants Hank brought into the dimension to build a new society that wouldn't fall under a dictatorship like Kang's was.
David Dastmalchian, who played Kurt in the first two films, plays a new character, Veb, in this film, due to the Wombats (Kurt, Luis, and Dave) not being present.
Katy O'Brian had previously portrayed Kimball, one of Nathaniel Malick's underlings, in the final season of Agents of S.H.I.E.L.D. before playing Jentorra here.
to Peyton Reed, Corey Stoll agreed to reprise the role of Darren Cross both to work with the Ant-Man crew again and because, as a comics nerd, he knew who M.O.D.O.K. was and loved the idea of getting to play him. Stoll himself noted that he really had fun working on Cross and Cassie's relationship, noting that he loved the idea of Cassie fighting the man who traumatized her as a child, but still having enough grace to encourage him to be a better person.