Anyone who knows anything about Mysterio knows that he’s not on the level. His whole deal is that he’s a villain who uses trickery to mess with Spider-Man’s perception of reality. Of course he wasn’t really a superhero. That said, was there more to him? This was after Marvel revealed that the Mandarin was a dopey actor and the Skrulls were sympathetic refugees. There had to be a twist for people who knew what to expect with Mysterio. Was he really just going to be the guy we know from the comics?
Before the Loki show was announced, Loki’s Avengers: Endgame cameo seemed too important to just be a throwaway moment. He escaped with the Tesseract and was a gigantic loose thread. Something was going to happen with him. Also, as explained in Thor: Ragnarok, Loki knows that his reputation on Earth is forever ruined. Therefore, what if Mysterio was really that Loki all along? It would add to Mysterio’s claims that he was from another Earth, as it would technically be true. What Loki wanted out of it was up in the air, but the setup was there.
Welp. Turned out Mysterio was just going to be the guy we know from the comics.
WandaVision Will Lead to the Mutant Age
Disney had bought Fox, and suddenly X-Men and Fantastic Four were on the table to use in the MCU. That’s easy enough for Fantastic Four, but not so much for X-Men and mutantkind in general. After over a decade of worldbuilding, how can you simply state that mutants have been around all along? There needed to be a plot-driven catalyst for it. Considering the comics mostly wiped out the mutant race via House of M, a story where Wanda Maximoff went insane and created a new reality with her powers, perhaps they could do the opposite with the MCU?
WandaVision was a show where Wanda was using her powers to create a new reality. It was a show that made vague allusions to House of M and made a very blatant meta reference to the Fox X-Men Cinematic Universe with the recast Pietro Maximoff. Wanda even created her own children who had powers and a sense of self. If there was ever an excuse to go big and introduce mutants to the MCU, this was the time.
The Engineer is Somebody Major
I could make most of this list just WandaVision theories, like what people thought was going on with the mysterious beekeeper and the reaction to Paul Bettany’s joke about acting with someone he’s always wanted to do a scene with (being himself in the Vision vs. Vision battle). People did go a bit overboard with the guessing games, but sometimes the setup feels so blatant that it’s hard to blame viewers for thinking something is up.