Bryan Andrews served as showrunner and director, with Wells as head writer.

The series features an ensemble cast including Awkwafina, David Harbour, Simu Liu, Elizabeth Olsen, Randall Park, Florence Pugh, Hailee Steinfeld, Dominique Thorne, and Iman Vellani, reprising their roles from previous MCU media, alongside Todd Williams.

[1] Additionally, Hudson Thames reprises his role as Peter Parker / Spider-Man from previous MCU media.

[5] Other characters confirmed to be appearing in the series include survivors Death Dealer,[1] Blade / Moon Knight,[6] and Xu Wenwu,[7] as well as zombies Clint Barton / Hawkeye, Steve Rogers / Captain America, Emil Blonsky / Abomination, Ava Starr / Ghost, Carol Danvers / Captain Marvel, Ikaris, and Okoye.

[17] Marvel Studios president Kevin Feige and animation head Brad Winderbaum enjoyed that episode so much that they suggested the story be continued,[15] and development began after a positive fan response to the episode.

[8] Winderbaum called the series "pretty intense" and compared the level of violence to the Marvel Zombies comics.

[21] Andrews noted that the TV-MA rating meant they "don't have to pull punches.

"[15] In November 2023, Iman Vellani said she was reprising her MCU role as Kamala Khan / Ms. Marvel in the series; she had already completed her voice work by then.

[4] In November 2024, several other actors were revealed to be reprising their MCU roles in the series: Awkwafina as Katy, David Harbour as Alexei Shostakov / Red Guardian, Simu Liu as Xu Shang-Chi, Elizabeth Olsen as Wanda Maximoff / Scarlet Witch, Randall Park as Jimmy Woo, Florence Pugh as Yelena Belova, Hailee Steinfeld as Kate Bishop, and Dominique Thorne as Riri Williams / Ironheart.

[5][23] The series features the same cel-shaded animation style as What If...?, with character likenesses based on the actors from the films.

[27] The series was discussed during Marvel Studios Animation's panel at the 2022 San Diego Comic-Con, when artwork of the characters was revealed.

[1] Andrews and Winderbaum promoted the series during Marvel Studios Animation's panel at the D23 convention in August 2024, where footage was shown.