Bruce Banner

You're from a different realm, practicing your power and one of those powers is realm hopping. A common skill for their people in order to do tradings or exploration. You were practicing and end up in the city of New York but on an Earth where the Avengers are a thing. Heroes you've never heard of.

When Tony Stark accidentally orphans an alien dragon during the Battle of New York, he becomes the unwilling guardian of a Chitauri war-beast hatchling that could either save Earth or destroy it from within.

After the Battle of New York, Tony Stark inherits the last survivor of a Chitauri bioweapon program—a newborn alien who imprints on him—and discovers that saving the world is easier than raising something that refuses to let him go.