'Imprisoned' is a double-edged sword. It's an okay story filled with good and bad moments. It's not bland, but it's definitely not exceptional. I don't like reviewing episodes like this. But I'll give it a try.
The story begins nicely (in a narrative sense). While camping in the wilderness, the gang comes in contacts with the war for the first time in the form on an oppressed mining town. Their entrance ticket to the town's problems is a young earthbender named Haru, one of the most confusing characters of the show. Haru secretly practices earthbending, admires his father's courage and defiance, and complains about the town's inhabitants being cowards - yet he does nothing himself. No underground resistance, not asking willing strangers for help. I can sort of see where his reputation of being a pansy comes from, notwithstanding his feminine voice.
The whole ordeal of Haru's capture is pretty heavy. The man Katara and Haru rescue turns traitor, and the silent message between Haru's mothers and Katara is one of, if not the most powerful, scene of the episode. The following faux earthbending scene is pretty stupid in comparison.
Once on the rig we are presented with the cliche-cruel warden, who nevertheless has a cool voice. The introduction of Haru's father is yet another confusing scene. He seems to be the main link between guards and prisoners, and the charismatic leader. But he's not leading much; no resistance here, either. Moving on.
Katara's speeches... The first time I watched the episode, the speeches were quite cool, but then they turned a bit silly. Alright, pretty silly. I guess the inspiration effect dies if nobody reacts to it, not that there was too much to begin with. You still rule, William Wallace.
We see some more awesome earthbending (or, rather, coalbending) in the final mutiny. And Katara loses her necklace, only to be picked up by Zuko. Now, if that's not a good plot device for future encounters, I don't know what is.
To give this review a conclusion, 'Imprisoned' is a nice episode. Just nice, nothing too big. I had just hoped throughout the entire episode to see some cool waterbending from Katara, since the rig was out in the middle of the ocean. But that just didn't happen.
It's hard to rank Imprisoned among the best Avatar episodes. It's hard to even say that it's one of the more decent episodes. It is an adventure that seems mostly cliched, and it certainly doesn't utilize these cliches in any new or interesting manner.
The story of the episode centers on a small Earth Kingdom village that has been occupied by Fire Nation forces. To maintain their stranglehold on the town, the Fire Nation has shipped all the Earthbenders off to a metal rig in the middle of the ocean, where their bending powers are useless. Enter Haru, a young Earthbender whose father has been captured and sent to the metal rig. He lives in fear of being caught by the Fire Nation, and attempts to hide his skills when noticed by Katara, Aang, and Sokka. Ultimately, he is captured due to a good deed, and Katara formulates a daring plan to rescue him by being captured herself.
First of all, this episode presents some rather upsetting plot points that left me wondering just how stupid the Fire Nation actually is. Katara's plan is to pretend to be an Earthbender and get caught. She does so, and is shipped off without a second thought. Why didn't anyone notice that she's dressed in Water Tribe clothes? Do the Fire Nation soldiers simply not notice them? Are they also oblivious to the fact that her skin is an entirely different shade than everyone else in the village? It simply seems very convenient that they bought her flimsy display of 'Earthbending' and shipped her off without any questions.
Then we're treated with one of the cheesiest monologues in the entire series when Katara finally meets up with Haru, his father, and the other Earthbenders. She gives an impassioned speech that is pretty much every cliched "Your strength comes from within, so fight!" monologue put together. It fails to be inspiring, and at least in this aspect the episode does well: none of the Earthbenders care about her words, either.
The prison warden fails to be any better. An insipid and cruel man, he makes a point of reducing morale by... giving the prisoners speeches about how hopeless they are. He fails to seem truly menacing since his speeches also seem to be recycled from various inspirational films, except that he plays the role of the villain that convinces the heroes that they have no hope.
The episode picks up slightly when the Earthbenders ultimately find their spines and begin to fight back against their captors. The bending battle is interesting, but not one of Avatar's most memorable fights. Oh, and did I mention that we have to listen to Katara give one more inspiration mini-speech?
A lot of the themes in the episode are undermined by just how cliched the material is. At its worst the episode is cringe-worthy, and at its best it's mildly entertaining.