3. He Worships Tony Stark - And We've Already Seen Him Years Ago
No, this isn't the theory that Peter Parker is the kid we saw back in Iron Man 3. It's that Peter Parker is the kid we saw back in Iron Man 2, in just a brief scene with Iron Man. This is the child at the Stark Expo, wearing an Iron Man helmet, who is then helped out by Stark himself. What's more, this scene takes place in Queens, New York, which just so happens to be the hometown of Peter Parker. So the idea goes that Parker, already a fan of Stark and Iron Man, is helped by this hero. Thus, when he develops his powers, Iron Man is his superhero idol, so it's only natural that he'd want to be on his side. It's quite similar to the Iron-Spider idea, but more grounded in the history of the MCU, and fits with the timeline - if we assume that child was around 9-10 in Iron Man 2, he'd be the right age for Peter in this movie six years later.