Cassie was one of the 50% of people who survived the Blip by Thanos' snap. In the five years following the Blip, she grew up under the assumption that her father had also fallen victim to the snap, not knowing that he had been trapped in the Quantum Realm.
The emotion from Scott comes from a few different areas. On the one hand, he is thrilled to see that Cassie is alive and was not snapped by Thanos like Hope van Dyne, Hank Pym, and Janet van Dyne were. However, there is also some sadness to see that his little girl is all grown up now.
Subtly explaining the recast, Reed noted that he wanted someone "who could really hang with Paul Rudd and sort of not be left in the dust," mentioning that whoever performed as Cassie needed to be "sharp, and quick, and funny." He also praised Newton's athletic ability, referencing her world-class golfing and reasoning ...
With such a dramatic time span, the character obviously needed to be recast to accommodate Cassie's true age. Thus, Abby Ryder Fortson was replaced by Emma Fuhrmann to embody the teenage Cassie.
Since Cassie was among those who were not blipped, she aged five years. This put her character's age at 15 in the film, while the previous actress, Fortson, was only about 11.
EVERY BLIP SCENE IN THE MCU: 15 Scenes from 2018-2023!
Why is Cassie different in endgame and Quantumania?
Marvel Studios recast Cassie Lang for Ant-Man and the Wasp: Quantumania, choosing Kathryn Newton for a bigger and more recognizable star in the role. The decision to recast Cassie Lang was not unusual, as Marvel has recast other characters in the past, such as Bruce Banner and James Rhodey.
There are touches added in—like Cassie calling Hank "Grandpa"—that help to illustrate how close this family has grown in the time since we last met them.
Thor. While Steve Rogers gets the title of the oldest human avenger, Thor Odinson, as the mighty Asgardian God of Thunder, has a much longer life span than any of his Earth-born friends.
Thor is the oldest official Avenger at about 1,505 years of age. He mentions his age for the first time during Avengers: Infinity War, which would put his birth date around 518 CE.
The Council Of Kangs Exiled Kang To The Quantum Realm
Led by a trio of powerful Kang variants, including Immortus, the Egyptian Pharaoh Rama-Tut, and a version of the Scarlet Centurion, the Council of Kangs consists of a veritable army of conquerors.
Cassandra "Cassie" Lang appears in films set in the Marvel Cinematic Universe (MCU). She first appears as a child in the films Ant-Man (2015) and Ant-Man and the Wasp, portrayed by Abby Ryder Fortson. She later appears as a teenager in Avengers: Endgame, portrayed by Emma Fuhrmann.
The fact that Cassie Lang is 18 years old in Ant-Man and the Wasp: Quantumania further explains some of her life. There is no appearance by her mother or stepfather, so it is possible that Cassie has now moved out - even though she mentions that no one can afford rent right now.
Another possibility is that Maggie wasn't present solely because the events of Ant-Man and the Wasp: Quantumania happened in such a short amount of time that it was during a weekend when Scott had custody of Cassie. That would also explain the surprise birthday and why they weren't there.
Assuming Tony had survived Avengers: Endgame, the confrontation with Thanos would have still left him with medical problems. If he survived using the Gauntlet, he may have even lost his hand. He certainly would have needed long-term medical attention.
In Avengers: Endgame (2019), Fury is restored to life. He attends Stark's funeral and reunites with Danvers. In the post-credits scene of Spider-Man: Far From Home (2019), Fury is working in space on a space station, having recruited Talos and Soren to replace him and Hill and give Stark's glasses to Peter Parker.
Willows, who is portrayed by Leon Lamar. Born in 1919, Lamar is the oldest actor to ever make an appearance in the MCU as he is currently 104 years old. Leon Lamar aka Cornelius was born in 1919.
Shuri is 3 years older than Peter, having been born in 1998. However, that didn't stop many fans of the MCU from shipping the two characters together. It's easy to see why - they're both extremely intelligent, not always so good in social situations, and focused on helping their families.
While it is never addressed in-universe, MCU director Joe Russo confirmed Thanos was around 1000 years old in 2012's The Avengers when he first appeared in the MCU. Based on that, Thanos is younger than Thor and Loki, which, if revealed in one of the past two Avengers films, might have proven itself to be distracting.
In Thor: The Dark World, Odin makes it clear that they “are born, they live, they die, just as humans do”, to which Loki replies that “give or take, 5000 years” – so taking that into account, Odin was at least 5000 years old when he died in Ragnarok.
When Kang the Conqueror finally shows his face to Janet van Dyne and her family, he refers to Hope as "Jellybean." This affectionate term is usually only used by Janet when speaking to her daughter, but Kang's use of the nickname shows the bond that he made with Janet when he was first exiled to the Quantum Realm.
Granted, Hope (Lilly) isn't referred to as Cassie's (Kathryn Newton) stepmom, and Hope and Scott (Paul Rudd) aren't officially married, as far as we know.
When the three are restored to life, Van Dyne joins the Avengers in a battle against an alternate Thanos. Afterwards, she heads the Pym van Dyne Foundation, continues a relationship with Scott Lang, and becomes a step-mother to Cassie Lang.
