The right to bear arms: 'Black Widow' actor claims he's the very first mutant in the MCU

If you think Black Widow is just a small potatoes adventure that simply fills in much-needed backstory for Natasha Romanoff's character, think again. With one little throwaway line spoken by David Harbour's Red Guardian around the one-hour mark, the movie could prove to be way more important to the larger blueprint of the Marvel Cinematic Universe than previously imagined.

We're referring to Shostakov's introduction at a maximum security Russian prison where the washed-up hero of the collapsed U.S.S.R. spends his days arm wrestling fellow inmates, or else regaling them with apocryphal stories about run-ins with Captain America in the 1980s (when Steve Rogers was still frozen). The only prisoner to call Alexei on his grandstanding is a beefy man named Ursa, played by the world's tallest bodybuilder and actor, Olivier Richters.

For the uninitiated, that name probably doesn't mean much. But for longtime Marvel mavens, the name "Ursa" immediately sticks out as a very obvious nod to the comic book character of Ursa Major, (aka Mikhail Uriokovitch Ursus), one of the Soviet Union's very first mutants, who has the ursine ability to transform himself into a massive, talking bear. See where we're going with this? The MCU may have quietly introduced its very first mutant in anticipation of eventually bringing the X-Men into the fold.

Credit: Al Milgrom / Frank Miller / Marvel

"After two years, I can finally tell who my character is: Ursa Major the first mutant (X-Men) to appear in the Marvel Cinematic Universe," Richters claimed on Instagram. "Ursa is part of the Winter Guard, noted for being Russia's answer to the Avengers. His power transforms him into an incredible bear, transcending the Hulk in size. Ursa appears many times in the comics fighting Wolverine and the Hulk. When production on set told me who I really was in Black Widow, I let some tears in my hotel room, because my movie dream became true: being a official comic super Hero. I can only hope Marvel will bring back Ursa in full form."

Now, we should take all of this with a grizzly-sized grain of salt. Ursa, who gets his wrist broken by Red Guardian, could just be a fun Easter egg for longtime fans of the Marvel Universe in the comics. Still, it's not a bad way to start paving the road to the 20th Century Fox properties, so they don't just come out of nowhere. Fans already got an exciting taste of the two studio universes colliding when WandaVision brought in Evan Peters as Quicksilver. Sorry, we mean Bohner.

With small hints here and there — like Ursa being part of its canon — the MCU should have a much easier time convincing fans that mutants have been walking around in plain sight this entire time.

Black Widow is now playing in theaters and on Disney+ Premier Access.