Avengers Doomsday: Kathryn Newton Reveals Not-So-Secret Return As Cassie Lang

The

list of actors appearing in Avengers: Doomsday got a bit longer. A day after footage from the Marvel film was showcased at CinemaCon 2026, actress Kathryn Newton took to social media to announce her part in the film. She will join Paul Rudd’s Ant-Man in the superhero sequel. She plays his daughter Cassie Lang and was last seen in the 2024 film Ant-Man and the Wasp: Quantumania. Her appearance starts off lots of theories of what it could mean for the future of the Marvel Cinematic Universe (MCU).

Cassie Lang will appear in Avengers: Doomsday after all

On Instagram, Newton posted a video announcing her return to the MCU. Fans had long guessed that Cassie would be back, especially after Rudd’s Scott Lang had been confirmed for the film. In fact, Newton’s video is a cheeky response to the original reveal of the Doomsday cast. The actress reveals her own little director’s chair as Cassie Lang because her character will be small. She says in the video, “[It’s] tiny because Cassie Lang gets tiny.”

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Newton’s Cassie will join her father and the rest of the MCU superheroes to save the world from Doctor Doom (Robert Downey Jr). The Oscar winner who initially played Iron Man in the MCU is now returning as a new sinister supervillain.

At CinemaCon, attendees already got a glimpse of Scott, aka Ant-Man, kissing Cassie on the head in a special trailer. Other superheroes in the supersized film include Captain America (Chris Evans), Thor (Chris Hemsworth), Black Panther (Letitia Wright), Shang-Chi (Simu Liu), Professor Xavier (Patrick Stewart), Magneto (Ian McKellen) and Gambit (Channing Tatum), amongst others. Directed by Joe and Anthony Russo, Avengers: Doomsday is slated to release in theatres on December 18, 2026.

Young Avengers introduction?

The Ready or Not 2: Here I Come star is the third actress to play Cassie in the MCU. Abby Ryder Fortson and Emma Fuhrmann played younger versions of the character in previous films. The actress’ involvement hints at a possible Young Avengers storyline in the MCU. Cassie could be joined by characters Ms. Marvel aka Kamala Khan (Iman Vellani) and Kate Bishop (Hailee Steinfeld), who later go on to form the Young Avengers. A Disney+ series featuring the characters is rumoured to be in the works. The characters are also expected to be back in the Doomsday sequel Avengers: Secret Wars in 2028 to play a larger part.