If it wasn’t for William Hurt’s Thaddeus Ross making his return in Captain America: Civil War, then there would be absolutely nothing that connects The Incredible Hulk to the rest of the Marvel Cinematic Universe. Since then, the 70 year-old has gone on to show up for cameos in the Avengers: Infinity War and Endgame double header, but he’ll get his most substantial supporting role in over a decade when Black Widow finally hits theaters next May.
Ross’ part in the prequel is still being kept under wraps, but a new theory claims that he could be revealed as a HYDRA sleeper agent, which would mark a huge development in MCU canon given that he was the United States Secretary of State when audiences were reintroduced to the character in Civil War.
As per the theory, an Easter Egg in The Incredible Hulk tying the movie to Captain America: The First Avenger is the key, as it establishes that Ross was trying to replicate the super solider serum at HYDRA’s request, which would also fit in with The Winter Solider‘s revelation that the nefarious organization had infiltrated every level of government.
Ross is also very anti-Avengers as the Sokovia Accords will attest to, so he might have ulterior motives in mind when it comes to his involvement with Natasha Romanoff in Black Widow. Hurt is clearly being de-aged for the movie, so we may be delving into events that happen much earlier in the timeline that tie Ross to Red Guardian, one of the only known super soldiers that survived the experimentation process.
The theory goes on to say that Ross intentionally divides the Avengers in Civil War for his and HYDRA’s benefit, and it would certainly be easy to imagine him being revealed as a sleeper agent in Black Widow due to his hatred of Bruce Banner and the offer of being tasked with taking down the rest of the world’s most well-known superheroes looking too good to turn down.