Until thousands of years later, when the Nine Worlds are approaching Convergence, allowing willy-nilly transfers of objects, matter and people betwixt and between such worlds.
Thor (Chris Hemsworth, who seems to enjoy this guy) and his estranged mortal love, Dr. Jane Foster (Natalie Portman), must figure out a way to keep this chaos from giving the Dark Elves a second crack at Doomsday.
Thor's evil half-brother, Loki, figures in all this, and Tom Hiddleston turns his third turn as the character ("Thor," "The Avengers") into a vamp. He downplays his prior villainy — "I really don't see what all the fuss was about" — talks up his conjuring skills ("If it was easy, everybody could do it") and finishes one trick with a "ta-daaaaa!"
Portman's Dr. Foster slaps Thor for not calling — "I saw you on TV. You were in New York (in "The Avengers")!" — and melts even when Odin grumpily dismisses "this mortal."
Dr. Foster's sidekicks — the Swedish scientist Selvig (Stellan Skarsgard) and the dizzy intern Darcy (Kat Dennings) — land laugh after laugh, with Skarsgard a hilarious nude and Dennings a delight every time she opens her overripe mouth.
A bit about Jane dating Chris O'Dowd doesn't work. The battles include laser-rifle firefights and spaceship dogfights, but the whole thing degenerates into yet another series of epic Earth-shaking digital brawls, the undoing of such promising fare as "Man of Steel."
Still, the lighter touch pays off with Marvel Universe cameos, running gags and the sense that things won't get serious until Captain America has his own movie. Again.
And like the half-villain/half-brother says: If it was easy, everybody could do it.