Thor: Tales of Asgard (not rated)
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This is a direct-to-video movie that came out in 2011, about a month after the live-action movie Thor hit theaters. I don't think it's really part of the same continuity as that movie, but I do think you could probably appreciate it a bit more if you've seen that than if you haven't. Anyway, I liked this more than I expected to. It's not great, but I do think the plot is more complex and a bit deeper than I expected it to be.
It begins with a cocky teenage Thor having an exhibition match against some of Asgard's best warriors, and of course he beats them. But later Sif tells him they had to let him win, because he's the son of Odin. And she proves her point by easily beating him in an impromptu match after clearly giving him the advantage. So, with his confidence shaken, he goes to Odin and asks if the warriors let him win, and Odin admits that they always do. Of course, this makes Thor desire to prove himself, so he convinces his brother, Loki, to stow away with him on a ship the legendary Warriors Three are using to sail to Jotunheim, realm of the Frost Giants. Supposedly they're going to look for the sword of Surtur, an incredibly powerful weapon that had been lost during a battle between Odin and Surtur, years ago. No one's ever found the sword, but Thor is determined to do so. Meanwhile, Sif leaves Asgard to train with the Valkyries. Um... Thor and company do eventually find the sword, and that leads to some seriously bad stuff. They inadvertently cause a major incident with the Frost Giants, which could lead to war. They also piss off the Valkyries (though that's not difficult, because the Valkyries are very militantly misandristic); luckily, Sif rejoins her friends. However, neither the Frost Giants nor the Valkyries turn out to be the main antagonists in the story, but I don't want to spoil who does. Nor do I want to reveal how it all ends.
Anyway... the movie has plenty of action, some heavy lessons for Thor to learn, okay animation, some mildly amusing bits (and some bits that are trying to be amusing, but fail). And I dunno what else to say.