Trivia: Stan Lee makes his usual cameo, this time as a patient at the asylum where Selvig is being held.
Trivia: The kiss between Thor and Jane after the credits doesn't actually feature Natalie Portman - due to scheduling issues she wasn't available, so Chris Hemsworth's wife Elsa Pataky put on a wig and filmed the scene.
Trivia: Stay during the credits for a scene part way through and another one at the end.
Trivia: Director Alan Taylor has stated that he wasn't completely pleased with how the finished film turned out. His initial vision for the film was more whimsical, while Marvel instead wanted something more stark and dark to contrast with the vibrant first film. Several major plot points were also changed in editing and reshoots to accommodate planned future storylines. An example is Loki, who was originally killed off in the first cut, but is shown to have faked his death in the final cut.
Trivia: Thor appears to lose his hand. Someone's lost a limb in nearly every MCU film since Iron Man 3.
Chosen answer: As seen in the film, the portals are in flux. They are constantly activating and deactivating, potentially pulling items through from one dimension to another.
MasterOfAll