From the very start, the Marvel Cinematic Universe made its Stan Lee cameos a signature part of its films. He always appeared for a quick gag or had a punchy joke at the ready, but the legendary comic book writer's appearances seldom had much influence on the plot beyond a wink to the audience.
The two biggest exceptions to this stand out among all the rest, however, and, by looking over the recently released The Wakanda Files, it's clear that his otherwise harmless presence in the films should have had major consequences.
In only the second installment in the MCU, The Incredible Hulk, the franchise broke away from the tradition of Stan Lee cameos that had little material consequence to the events of the film itself. Whether it was in Sam Raimi's Spider-Man films or the X-Men trilogy, Stan Lee always appeared for a brief spot that ultimately wouldn't mean much if the scene were cut. However, in The Incredible Hulk, his cameo provides the impetus for much of the plot -- and it all goes back to a bottle of soda.
Hiding out from the government following his transformation, Bruce Banner worked as a low-level employee at a bottling factory to evade detection. But when he accidentally sliced his thumb open and unwittingly spilled some of his blood into a bottle of soda, the bottle made its way to the home of Lee's character, who drank it, only to contract radiation sickness shortly after. As it turns out, the radiation sickness is what clues Thunderbolt Ross in on Banner's location, meaning Lee's involvement greatly impacted the film's events. Now, though, The Wakanda Files informs fans that Lee's impact should have been even greater than that.
The book, released to give fans further insight into the science and world of the MCU, states that the Pingo Doce bottle contaminated with Banner's blood showed a presence of "trace amounts of unidentifiable radiation," and that its consumption leads to Lee's character, seemingly an innocent Milwaukee man, to be treated for "effects of radiation poisoning." However, using what was revealed later in the MCU, Lee's character was not just some innocent man -- he was an informant for the Watchers.
Known to comics fans as surveyors of all existence, the Watchers are the iconic bald giants caught speaking with a spacesuited Lee in a cameo in Guardians of the Galaxy Vol. 2. If Lee was truly an alien, then the analysis of his blood should have revealed as much to human civilization at a point relatively early on in the MCU. With the events of The Incredible Hulk far predating the Chitauri invasion, that information should have been a bombshell to the governments of the world.
At most, this excerpt may indicate that Lee's character is not actually an alien at all. This would help explain why he needs the spacesuit when the Watchers do not, and it could be that they merely recruited his character seen in so many of the MCU films for his firsthand familiarity with so many of Earth's most significant figures. Furthermore, it could even indicate that all of Lee's cameos are not as connected as the Watchers scene led fans to believe, or that the events of The Incredible Hulk are, in fact, non-canonical, given that the film is often treated as the black sheep of the MCU.
On the other hand, it's always possible that there is little connective tissue between these events at all, with little foresight or planning going into how they fit together. So much of the fun in the MCU comes in making the puzzle pieces work, however, and anything that does not fit becomes vastly more interesting once fans try to find the solution for how best it could fit. And, as it turns out, Lee's character getting blood work done may be one of the best examples of this.