TMDb/Avengers: Doomsday Movie Kathryn Newton returns as Cassie Lang in Avengers: Doomsday, joining the MCU's epic ensemble. Premieres December 2026. April 18, 2026 AceShowbiz - Avengers: Doomsday will see the return of Kathryn Newton as she reprises her role as Cassie Lang in the Marvel Cinematic Universe. Following her appearance in the 2023 film Ant-Man and the Wasp: Quantumania, Newton is confirmed to join the ensemble cast of this highly anticipated superhero movie. The film is scheduled for release on December 18, 2026, continuing the expansion of the MCU's storyline.