I don't expect many people to buy into this one, and it's not like I expect it to happen myself, but wouldn't it be cool to finally see Spider-Man, Marvel's most iconic character who has long been denied entry to the party, finally be allowed to hang with Iron Man and co? Granted, Sony owning Spider-Man's film rights is likely the reason it hasn't happened so far, but given that the Oscorp building very nearly appeared in The Avengers, that would suggest that Sony and Marvel aren't too averse to working together; the only reason the building didn't appear is that Marvel Studios had already rendered the New York skyline when the idea was suggested. Given that The Amazing Spider-Man 2 is shooting as we speak, due for release next year, it would make sense to give Peter Parker a leg-up by teasing the idea of him joining The Avengers in Iron Man 3. Perhaps Tony nearly runs him over when he's skate-boarding along and Peter leaps out of the way? Something as simple as that would put the idea in our minds, and they could then build on this in ASM2 before he joins the line-up properly in The Avengers 2. It probably won't happen, but we can dream, right?