The introduction of zoopathy in Natasha Romanoff's origin story to the big screen. The first film of the MCU's phase 4, Black Widow initially translates as a gritty spy endeavor a la The Bourne Identity before unfurling into a typically superpowered Marvel Cinematic Universe installment.
Midway through its runtime, Black Widow introduces a rudimentary zoopathy to the MCU, which grants one the power to mentally control animals. Former Black Widow Melina Vostokoff reveals she has installed a cognitive hub inside her pet pig Alexei's brain, which allows her to command the animal at will. While some facets of this technology are shown to be still reliant on machinery across Black Widow's plot, this is a nexus moment for the MCU, given the entirely new power on display despite its rather low-key introduction.
The wider implications of zoopathy being present in Black Widow is that it marks a gateway for bringing other Marvel characters who have this power into the wider MCU. Squirrel Girl is the pick of the bunch here, as her ability to commune with squirrels can now be explained within the pre-established confines of Marvel's Cinematic Universe. As power manifestation is currently not canon in the MCU, Squirrel Girl's best route to inclusion in the franchise is to have her zoopathy, as well as her other superpowered qualities, bestowed upon her by technology.
The outpouring of for Milana Vayntrub's leaked character footage as Squirrel Girl from the canceled New Warriors pilot suggests Black Widow's inclusion of zoopathy could not have come at a more opportune time. In the Marvel Comics canon, Doreen Allene Green, aka Squirrel Girl, manifests her powers at ten, presumably through a dormant mutant genome. Green discovers she can talk to squirrels before later sprouting an impressive prehensile tail and the ability of super-strength all explained before Squirrel Girl's 14th birthday.
However, this random exposition of superpowers is not a normal occurrence within the current state of the MCU, leading many to assume the rodent champion would not be appearing in the franchise any time soon. Black Widow establishing zoopathy completely flips this theory on its head, as the MCU phase 4 has now been given a clear way for individuals to command and commune with animals at will. The cognitive hub technology introduced by Vostokoff in Black Widow ensures that Squirrel Girl's complete power set is now realistic by MCU standards, with both her squirrel and strength abilities proven to be augmentable traits within Phase 4's setting.
Squirrel Girl's origin story will still need to be tweaked, of course, given her original mentor Iron Man is now dead after his snap against Thanos in Avengers: Endgame. While Green may need to be fitted with a darker backstory that points to genetical engineering in order for her powers to conform to MCU guidelines, Black Widow's events mean Squirrel Girl's path to the MCU now looks cleared of the roadblocks that hampered her character for such a long stretch in the Marvel think tank.
