India, July 22 -- The Marvel Cinematic Universe has built a reputation for rewarding eagle-eyed fans. Nearly every trailer hides clues, references and comic book callbacks that become important later.

The first trailer for Avengers: Doomsday is no exception. The two-minute preview is packed with hidden details that hint at the film's story, introduce comic-accurate costumes and tease Doctor Doom's arrival.

The trailer shows three connected Earths heading toward Avengers Tower. Fans believe these represent Earth-616, Earth-828, and the X-Men universe crashing into each other.

If true, the scene could be teasing an Incursion, where multiple universes collide, a storyline lifted directly from Marvel Comics.

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