SPOILER ALERT ... and not the usual 'spoiler alert,' where I don't tell you anything you don't already know is gonna happen; but something mysterious that will change how you watch the movie (making it a different movie almost ...)

See, it weaves smoothly into the MARVEL universe (changing the name of 'the 5 years that people had been gone because of Thanos's snap' from "the decimation" to "the blip"). In fact, the main antagonist whom they call "Mysterio" uses the recent Avengers-activities as a sort of 'cover' for his attempt to fool the world into ... worshiping him?

"Mysterio" is a 'character' put-together by a team of Tony Stark''s former employees with their leader----who also ‘plays the part’ of Mysterio … a (fictional) being from a (fictional) parallel universe whose Earth was permanently decimated by the (fictional) Elementals.

There … a REAL ‘SPOILER,’ as--before I learned that Mysterio was “fictional” (like Ben Kingsley’s "Mandarin" in IRON MAN 3)--I thought he was really a Thor-level superhero … heck, even Nick Fury & Agent Maria had practically installed him as a member of The Avengers!

But do stay for the post-credits scene, as it sets up a major conflict Spiderman will have to deal-with in his next movie (or more).