After the 5 episode mark, Avatar: The Last Airbender really starts to heat up.
By this point, Avatar has enough episodes out to start to cater to its own audience, rather than the Nickelodeon audience. The end result is that, while still targeted toward a relatively young crowd, Avatar isn’t all about penguins and games anymore.
While the trio still haven’t reached the North Pole by episode 12, the rest of the plot really kicks into motion. I’m not sure if this is a result of the plot taking too long to get started or going too quickly, but in any case the reality of being the Avatar quickly catches up to Aang.
Episode 6 focuses on a Katara-led scheme to free an Earthbender who was imprisoned due to an idea that was Katara’s inspiration. You know the deal: Character A suggests Character B do something else because it’s the right thing, even though everyone else Character B knows would say it’s a dumb idea because Evil Overlord punishes people for doing that. Well, Katara is Character A, and she gets herself arrested to save Character B. She finds herself in for a shock as she winds up on a prison barge with a bunch of Earth benders who are too broken to try and free themselves, despite her inspirational speeches. This is a largely Katara-focused episode, though it really gets the story of the Avatar as a savior moving as well. Personally, I would have gone back to the village and shown that old man what I think of snitches.
In what’s technically a two-parter, the group comes across a village being attacked by something that seems unique in the world of Avatar: a spirit that attacks with a non-elemental attack (think Hyper Beam or Aeroblast and you’re along the right track). Aang comes into his own as a protagonist when he confronts the creature. In a sequence of events that’s as yet unrivaled in the series and therefore remains a mystery, Aang is dragged to the spirit world, meets the animal companion of Roku, his predecessor as Avatar, returns to his body, talks the spirit into being happy, and returns all of the people kidnapped by the spirit. Um… yeah.
The reason I say the heavy part of the plot- that of Aang as Savior of Everything- is the second part of the two-parter. This episode is dark as shit and I’m lovin’ it. Aang must make it to a temple in Fire Nation space, where he speaks to Roku. Zuko’s ship follows them, where the Fire Nation officer from the earlier episodes gives chase instead of capturing the banished Zuko. After some difficulty, as most of the Avatar’s attendants, who are supposed to be loyal to Aang but are instead loyal to the Fire Lord (who doesn’t have a name it), Aang makes it into the innermost chamber. Roku gives him a tale of the MacGuffin of impending disaster, putting a one year time limit on this three season series, and then they destroy the temple after a suitable moment of suspense.
In addition to pushing tension on Aang to the extreme, this episode is notable because it’s the first where viewers might find themselves cheering Zuko on as he deals with the other guy (I should learn his name). Earlier on (I think it was episode 7) Zuko’s uncle Iro becomes the prisoner of the Earth Kingdom, which was a similar first, although Iro was always the most sympathetic of the Fire Nation characters. These guys have a confrontation with the heroes and some pirates in the next episode, take a break, and then in episode 12 we’re treated to a lesson on how Zuko got his scar.
Episode 10 is notable because for the first time we’re treated to someone other than the Avatar Trio and the Fire Nation that are actively involved in combat. We meet a guerrilla group led by a man named Jet, presumably a teen like Sokka and Katara. This episode is a largely Sokka focused episode, including Sokka not only leading the action but also taking part in a battle as a fighter (though he maintains his comedy relief role) without any sort of cowardice.
My last comment, on Episode 12, is that we also learn a bit about Aang’s backstory. This is where the series starts to cement itself- an all flash-back episode is not easy to pull off. We learn that, despite his tremendous progress in airbending, Aang had only known he was the Avatar for several days prior to his entrapment in the glacier. He shows he’s made progress even since that time, as he avoids the same situation that led to his hibernation before. It’s a mostly dark episode, but it ends on a light note, both for Aang and Zuko.