The road to the screen for an MCU tentpole like 'Avengers: Doomsday' is often complex, with scripts evolving throughout production. Directors Anthony and Joe Russo have previously acknowledged their improvisational approach, even confirming that filming for 'Doomsday' proceeded without a fully locked script. This dynamic environment, coupled with the film's ambitious scope – including Robert Downey Jr.'s return as the iconic villain Doctor Doom – naturally opens the door for various creative inputs.

Officially, the WGA has designated Stephen McFeely and Michael Waldron as the credited writers for 'Avengers: Doomsday.' McFeely is a familiar name to Marvel fans, having co-written major entries like 'Captain America: The First Avenger,' 'Avengers: Infinity War,' and 'Endgame.' Waldron, known for his work on 'Doctor Strange in the Multiverse of Madness' and as the creator of the acclaimed Disney+ series 'Loki,' brings his own distinct voice to the project.

However, the intrigue deepens with rumors surrounding the involvement of actors Ryan Reynolds and Hugh Jackman in the script's development. A reliable Marvel scooper on X/Twitter shared, "I recently learned through their production companies, Ryan [Reynolds] and Hugh [Jackman] may get some form of screen writing credits on '[Avengers:] Doomsday,' too." While actors often contribute through ad-libbing, a formal writing credit suggests a more significant role.

This potential recognition could come in the form of the WGA's 'additional literary material' (ALM) credit, a category introduced in 2022. This credit acknowledges individuals who provide writing services that don't meet the criteria for primary authorship but are nonetheless valuable. While an ALM credit doesn't come with residuals, it allows contributors to list the experience on their resumes. For instance, 'The Fantastic Four: First Steps' saw seven writers receive ALM credits, including 'Doomsday' screenwriter Michael Waldron himself.

Ryan Reynolds is no stranger to screenwriting, having co-written 'Deadpool 2' and the upcoming 'Deadpool & Wolverine' alongside Rhett Reese and Paul Wernick. His experience in shaping character dialogue and narrative, particularly for his comedic and meta-aware roles, makes his rumored involvement plausible. The extent of Jackman's potential contributions remains to be seen, but given the collaborative nature of major blockbusters, it's not unheard of for actors to influence their characters' arcs or dialogue significantly.

As 'Avengers: Doomsday' heads towards its release on December 18, 2026, the final list of all credited writers, including any ALM recipients, will eventually be unveiled. This development underscores the often-unseen collaborative effort behind Hollywood's biggest productions, especially within the ever-expanding Marvel Cinematic Universe.