This episode's protagonist is the show's antagonist. And even though this episode can be considered a filler, it is still extremely heavy in the character department. It includes such a large amount of character revelation and character development that it doesn't only give us great insight into Zuko's personality and history, but he is now by all right, even to those who doubted it, a main character.
The first thing to note is that this is the first episode devoid of the gang. Indeed, except in various flashbacks, Zuko is the only recurring character to appear in this episode. And therein lies the key: We get a very complete characterization of Zuko with the help of other characters, who in turn get characterized themselves. It's a great win-win situation.
True to his last appearance in 'Avatar Day', Zuko is now, as the title suggests, alone, trying to find his own way in the world. But being isolated also brings back memories. This episode is split into two parts, one being the present events in the Earth Kingdom village, the other one being Zuko's memories of his past at the Fire Nation court. It is impossible to say that either one of these two is the more important one; both of them together make a complete whole.
We learn a great deal about some notable events in Zuko's childhood, mainly his father's rise to power and his mother's care. And while the grownups scheme around, we also find out his relationship with Azula. One thing that was done very well is the spacing of these flashbacks: They are all tied to the events in the present and are shown beforehand, sort of as an explanation of Zuko's motivations in his actions.
This is an episode that, more so than many others, displays the grand art prevalent in the series. Both lines of events are shown in almost equal quality and sharpness (meaning the flashbacks are not specially hued or hazy), making both of them equally important. Indeed, most of the scenes in the village are kept in very simple and radiant red and brown tones, whereas the flashbacks seem more tranquil, but also mysterious with their darker hue. It is also the art that creates a very surrealistic feel that permeates this episode.
In terms of music, it stays very low-key throughout the episode, and only in the very end during the fight does it churn up the action. However, the biggest musical outburst comes when Zuko firebends and steps out of the flames, with the Fire Nation theme blaring away in the background.
What is interesting is that Li's father seems to trigger these flashbacks with his saying about a man's past being his own business. While these certainly are words of wisdom, this episode shows just how hard a past like Zuko's is to contain, and that it will eventually and violently erupt and catch up with him. He is also judged by who he is, not what he does. This ends the episode the way it started: Zuko riding away alone.
One last thong to say is that this episode's bad guys belong to the show's good guys, the Earth Kingdom. This little fact makes the world much less black and white and much more plausible.
Overall, this is a very fantastic episode, and while many might consider it a Zuko-characterization episode, it is really much more than that. It is a history lesson of the intrigues of the Fire Nation court, an introduction of Fire Lord Ozai (as a real character, not just a figure) and Ursa, and, last but not least, an artistic masterpiece.
This episode completely breaks the mold for an action cartoon by focusing completely on one of the main antagonists in a serious light. "Zuko Alone" does not mention the main protagonists at all, a feat not even two of my favorite animated action shows, "Cowboy Bebop" and "Full Metal Alchemist", are able to claim.
Zuko, when we first saw him, seemed to be the generic villain but soon we saw what he really was, a troubled young man still trying to get love and acceptance from his cold and distant father. "Zuko Alone" goes deeper than "The Storm" cared to and we learn much more about what made Zuko the way he is.
While Zuko helping the local Earth Kingdom peasant family was the event happening presently the flashbacks are what make this episode so grand. The present tale wasn't uninteresting at all though because it showed us that Zuko wasn't pure evil, not mugging a couple with a pregnant mother and trying to bond with the local peasant boy that lost his older brother in the war. What I find most spectacular of the present section is that neither Zuko or the Fire Nation himself are the antagonists but a band of corrupt Earth Kingdom soldiers who are extorting supplies from the defenseless Earth Kingdom villagers for "the war effort" which is really just for their own selfish needs. It really gives a realistic look at war because even the most righteous side of a war isn't completely safe from corruption.
Now to the flashbacks which I previously stated are the highlight of the episode. Avatar shows us how much entertainment and information we can get from flashbacks when the majority of recent television show flashbacks are just to fill up space and have no real relevance. Through these flashbacks we learn about Zuko's mother Fire Princess Ursa who at this time was of the very few that actually loved Zuko. Ozai is still seen as a cold and distant figure which could prove detrimental to the story in the long run but so far is permissible. This is also the episode where we learn about the death of Iroh's only son Lu Ten and Iroh's change in character which I hope leads to another episode like this. Iroh gives Zuko through mail an Earth Kingdom knife from an Earth Kingdom General that surrendered. On it is inscribed with the words, "Never Give Up Without a Fight"; Zuko keeps this with him on to the present.
Ozai is still power-crazed wanting to take the throne from his older brother, but their father, Fire Lord Azulon, refuses out of sheer disgust and swears that he will make Ozai feel the same pain Iroh is feeling right now. This leads to the darkest part of the episode and probably the show so far in which Azulon is found murdered the next day, Ursa leaving during the night telling a drowsy Zuko that she'll always love him, and Ozai ascending to the throne.
There is one major flaw to the flashbacks though that keeps the episode from getting an A+, Azula even as a child is shown to be a sadistic hell-spawn to the point when she shows utter glee over the death of Azulon and the disappearance of Ursa and revels in mentally torturing Zuko endlessly. That's just unrealistic and to me makes me think Azula is what Zuko is not, the clichéd "evil for the sake of evil" villain. People aren't born evil and children don't have a developed concept of good and evil, Young Azula clearly understands what she's doing and has an un-realistic enjoyment of it. That's the main reason I don't like Azula as a character, she's too evil to the point where I think it's becoming absurd. At least villains like Batman's The Joker have complete insanity for an excuse.
The ending of the present events ends in a more realistic and melancholy note, when Zuko reveals his true identity, the peasants force him out of the village, even though he saved the village from the corrupt soldiers. This really shows how a century of hatred and prejudice can override even the most righteous of deeds. "Zuko Alone" is truly one of the greatest hallmarks of the series and animated action in general.