9 Most Compelling Theories About Upcoming Marvel Movies
3. Hulk Went To Space
Bruce Banner is AWOL as of the finale of Avengers: Age Of Ultron, having admitted his love for Black Widow whilst acknowledging that he has a propensity of turning into a big violent green monster who smashes rather indiscriminately. So he flew away in a Quinjet which was later found crashed in the ocean.
The obvious assumption is The Hulk jumped out at some point and snuck off, perhaps so Banner can lie low in the jungle as he was at the beginning of the first Avengers film. A more outré theory floated by some fans is that the ship came trundling down after Banner shot himself into space, kicking off the long-rumoured Planet Hulk storyline.
In the comics, the constant danger of a Hulk caused Tony Stark and some well-meaning pals to jettison him into the cosmos. He later came back, having made a family on an alien world conveniently populated by Hulk-size aliens, for revenge. He won't be needing that if it's a self-imposed exile, but Hulk in space means a Guardians team-up, maybe?