It’s common for movies to be produced under a working title, a code name that is often meant to disguise the production or act as a placeholder for the movie’s real title before it is determined. Avengers: Infinity War, on the other hand, is already known as the name of the highly anticipated sequel, but now the production’s cover may have been blown.
The fourth Avengers movie will have a different subtitle from Infinity War, but with the third movie still in pre-production it is not even in need of a working title. Plenty of rumored details of Infinity War, have trickled out and it’s been speculated as to how the Avengers would reunite and what kind of role that Star-Lord (Chris Pratt) would play in the sequel, but what no longer needs speculating on is the movie’s working title.
Production Weekly has reported (via ComicBook.com) that Avengers: Infinity War is operating under the working title “Mary Lou.” The original Avengers was produced under the working title “Group Hug,” while Avengers: Age of Ultron had the working title “After Party.” What “Mary Lou” means to the production of Infinity War or the Marvel Cinematic Universe, if anything at all, is anyone’s guess.
Since the fourth Avengers movie remains untitled, you can expect that movie to have a different working title, even though the sequels will be filmed together. Marvel Studios head Kevin Feige recently said that the two movies will each feature their own separate plots and won’t necessarily be two parts of one story, so it would make sense for the as-yet untitled Avengers sequel to function as a separate production in terms of its working title.
Little is definitively known about Infinity War or the fourth Avengers movie, so it’s practically impossible to glean any sort of meaning from “Mary Lou” as its working title. It could very well mean nothing and exist as merely a red herring to prevent outside entities from uncovering “Mary Lou” as one of the MCU’s major productions. The working title is no longer a secret, but its meaning could forever remain a mystery.
“Mary Lou” will certainly invite a wealth of speculation among fans, especially as there are such scarce plot details about the movie available at this point. That could all prove to be a waste of time, as the working title could be effectively meaningless. But the Illuminati could be involved in Infinity War, so even the most harmless-looking details may turn out to have hidden significance. It’s likely that you’ll have to wait until Infinity War’s release to see if “Mary Lou” has any meaning at all.