Emma Fuhrmann played the now-teenage Cassie Lang in Avengers: Endgame (2019), but the role was recast with Kathryn Newton. Fuhrmann claimed on Twitter that she learned about being replaced when Disney released details of the film at their Investor Day in December 2020, and that while she was saddened, she was still grateful to have been a part of the MCU.
Scott's Ant-Man suit has been altered to include the classic chest pattern from the comics.
In an anonymous interview with Vulture, a VFX artist said that the quality of the effects of this film were sacrificed in favor of Black Panther: Wakanda Forever (2022): "In terms of priority, Wakanda Forever was definitely at the top of the list. All the money went to that. All the best resources went to that. It's understandable given the context - with Chadwick and everything and how well the first film did. But it did diminish the ability to carry Ant-Man all the way through. For Ant-Man, there were a lot of editorial changes happening toward the latter third and fourth of the project that were just too late. There's a point of no return. Why certain things were changed, why certain notes were nitpicked longer than they should have been - that's on Marvel. But it definitely did cause a lot of tension, turmoil, and weight on everybody at [company name redacted]. Unfortunately, it is noticeable that there were shortcuts. Certain things were used to cover up incomplete work. Certain editorial cuts were made to not show as much action or effects as there could have been - likely because there just wasn't enough time to render everything. There was a lot of shortening and rolling of shots (rolling is when you don't shorten or lengthen a shot - you just move it a few frames in the cut). It really did feel like certain scenes were trimmed or otherwise altered to either save money, save time, or cover up the inability to get it done."
(at around 19 mins) When Janet is explaining why the Quantum Realm didn't look like this last time, she briefly uses the phrase "Sub-Atomica", which in the comics is either a specific system in the Microverse visited by the Fantastic Four or simply Reed's name for the Microverse.
Mark Oliver Everett: (at around 3 mins) Frontman of the rock band Eels, cameos as a man asking Scott for a picture. Everett's father Hugh Everett III was the first to propose the many-worlds interpretation of quantum mechanics.
Ryan Bergara, Marielle Scott: (at around 3 mins) Co-host of BuzzFeed Unsolved and his wife cameo as two people who pay for Scott's lunch and raise a toast to him.