It is not usual that a character gets recast especially in the Marvel Cinematic Universe where one comes back for another project which is why it surprised many that Abby Ryder Fortson and Emma Fuhrmann were replaced by Kathryn Newton as Cassie Lang in Ant-Man and the Wasp: Quantumania.
Why Is Emma Furhmann Replaced by Kathryn Newton As Cassie Lang in Ant-Man and the Wasp: Quantumania?
To start, it was Abby Ryder Fortson that was first replaced by Emma Fuhrmann for the simple reason that there was a five-year time jump in the narrative when Endgame came into existence and Ryder was too young to play Cassie Lang once Scott Lang came out of the quantum realm.
But for Emma Fuhrmann, she was replaced by Kathryn Newton to play the role of Cassie Lang in Ant-Man and the Wasp: Quantumania. The decision of Marvel Studios was unveiled in 2020 when Kevin Feige officially confirmed the title of the movie for Phase Four of the MCU.
While Emma Fuhrmann is a rising star, Marvel Studios seemed to deem it fit to replace her as Cassie Lang with a bigger actress who is rising in the industry with Kathryn Newton for Ant-Man and the Wasp: Quantumania especially with Stature possibly arriving in the MCU.
It's not that Fuhrmann isn't good, it's just that since Cassie Lang is about to take a bigger step in the franchise, Marvel might have needed the extra kick for her character with an actress who already has more star power like Newton who has Detective Pikachu, Freaky, and Big Little Lies under her name.
There is also the factor of having a different director for both Endgame and Ant-Man and the Wasp: Quantumania. Peyton Reed may have a different vision for the third Ant-Man movie which would have Newton fit better as Cassie Lang.
Despite being older than Fuhrmann, Newton could still deliver the role of being a teenager with that fact that by the time Ant-Man and the Wasp: Quantumania arrives, Cassie Lang would still be a teenager and Newton's previous roles show that she could easily fit in playing a role younger than her age.
Anyway, this isn't the first recast that the MCU has had over the years with the notable ones like Edward Norton being replaced by Mark Ruffalo as Hulk, and Don Cheadle taking the mantle of Rhodey/ War Machine from Terrence Howard.
With the recast of Cassie Lang being on the early stage of Cassie's rise in the MCU, there's still time for Newton to own the role and make it hers.
See Kathryn Newton as Cassie Lang in Ant-Man and the Wasp: Quantumania in theaters on February 17, 2023.