Nick Fury is a spy above everything else. You don’t get to be the director of a top-secret organization unless you are the best at what you do. It is always expected that Nick Fury will have a backup plan for a back plan, and the new theory has come to light pointing out exactly what his backup plan was for the Avengers.
Nick Fury has repeatedly proved himself to be a character who always has a plan ready to go. As a spy, he deals with knowledge and information, something he likes to keep from his enemies, but actively seeks out himself, not just about his enemies, but also his allies and friends.
Stan Lee was Nick Fury’s Spy
Nick Fury has a host of informants that keep him in the loop about what has been going on. However, the one character that is often seen in the MCU is Stan Lee, whose cameos continued until his tragic passing in 2018. Up until then, Stan Lee was in every film that was made by Marvel Studios, from Iron Man to Infinity War.
The theory states that Nick Fury started working with Stan Lee when he was young, giving him a version of the super-soldier serum that keeps him from aging at normal human speeds. This allows the man to be present where Avengers and other MCU entities usually end up so that he can report whatever has happened with that particular character back to Nick Fury. Given that the character also had a presence in space, it is safe to assume that Stan Lee’s intel would have allowed Earth to establish SWORD.
The serum that Nick Fury gave to Stan Lee could be the Infinity Serum, one that slows aging.
Stan Lee might have been a double agent
While being a liaison of Nick Fury, feeding him information about the Avengers and other entities of interest, We see in Guardians of the Galaxy Vol. 2 that Stan Lee is also in touch with The Watchers, a race of aliens who watch and record the goings on of the universe. We see him giving them details about all that he has seen, in space and possibly even on Earth.
While this is the official explanation of Stan Lee’s character in the Marvel Cinematic Universe, it is also possible that Stan Lee was regaling this information to Nick Fury, keeping him informed at a more cosmic scale, such that he be prepared. One could also assume that the information about space that Nick Fury received could be his way of keeping tabs on Captain Marvel, whom he hoped he could help if the need arose.
