Cassie Lang is Scott Lang's little spitfire of a daughter. She hoped to become a superhero of her very own as a child, even if she ended her life as a partner in Ant-Man and the Wasp: Quantumania trailer.
Cassie, a congenital heart condition, is saved by Scott, who is able to save his daughter's life in 1979's Marvel Premiere #47.
Her Pym Particle experiments culminate in a lasting effect on the girl, allowing her to shrink and grow without the use of a suit. In May 2006's Young Avengers #6, she chooses Stature. She later changes her name to Stinger.
Cassie was initially played by Abby Ryder Fortson for the first two Ant-Man films. She was filled with excitement over her dad's superhero identity and just thought the world of her idol. She was kidnapped and threatened by Yellowjacket, and she defended him from the FBI. When things got tough for Scott, she said she meant Hope Van Dyne's Wasp.
Scott was trapped in the Quantum Realm during Thanos' run, resulting in another five years away from his daughter. Cassie was then a teenager (played by Emma Fuhrmann) when he returned during the Avengers: End Game.
Cassie, who is now playing Kathryn Newton, is said to be experimenting with the Pym Particles, as opposed to her comic book counterpart. The feeling she sends results in them being sucked into the Quantum Realm and confronting Kang.
Cassie's MCU superhero identity has been largely hidden from fans, but the new outfit is also revealed, potentially giving viewers a huge spoiler in the video. While Cassie wears a red suit similar to her dad's, the trailers show her wearing a purple suit similar to the one her comic book character wears as Stinger.