Tips & Notes on Writing & Playing Loki
Loki's teleporting may not be all that.
Many fanfictions portray Loki as popping up and off at a moment's notice. However, in Thor, while it is implied that Loki can teleport to other places if he really has to, the fact that he immediately switches to using the Bifrost after becoming king suggests that the methods he uses aren't precisely easy. Whether Loki can teleport under his own power is unknown. At the end of Thor and in The Avengers, he projects illusions of himself when he needs to communicate over long distances. It also appears that he is able to project at least one solid duplicate at a time in The Avengers, as he apparently used a duplicate to open and close the door of the glass cell.
If Loki were able to teleport as easily as is often portrayed, surely Thor would have said something about it when they had him in SHIELD custody - after all, he saw Loki appear in front of him when he was held by SHIELD in Thor, and he didn't seem too surprised, which indicates that whatever method Loki was most fond of using for getting around quickly, Thor was aware of it.
Loki can be quite polite and mellow when the situation calls for it.
Loki is a complicated fellow. He can kill without a second thought. He can break someone down just by verbally attacking their weak points and enjoy every minute of it. When pushed too far himself, he nearly breaks down in tears. But he can also be genuinely polite and soft-spoken, and can even relax a little and enjoy himself. If his lines in the underground lab are any indication, he's even in the habit of saying "please" to his subordinates. (However, if the cut scene in Thor is any indication, he isn't above playing petty pranks on them now and then, either.)
Asgard sew Loki's lips shut? Maybe not...
Many people have the Asgardians punish Loki by sewing his lips shut - and exactly how he's supposed to eat or drink is never addressed. But perhaps more importantly, is this something MCU!Asgard would actually do? In Norse mythology, Loki's lips were sewn shut by dwarves whom he made a bet with, not his own people. This also happened in the comics at one point, but then again, there are significant differences in Loki's characterization between the different media. Add to that the fact that Odin believed Loki dead - it would take a complete monster to easily dish out such a cruel and unusual punishment after such circumstances.
UPDATE: CONFIRMED!!! In the Thor 2 trailer, Loki is shown being held in a very clean-looking cell, and his lips are most definitely not sewn shut.
Loki is not "thousands" of years old.
The beginning of Thor explicitly takes place in the year 965. As of the time this is written (2012), that would be approximately 1047 years ago. When Odin found Loki, he appeared to be about three months old. Based on the fact that in the films the Norse stories were inspired by the Asgardians, and that Loki and Thor were very much adults in these stories (the illustration Dr. Selvig shows depicts Loki as an adult), we can conclude that neither Aesir nor jotnar take extremely long to mature.
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