Continuity mistake: When Azula is asking Zuko whether or not he thinks the avatar may have survived, Zuko goes into a flashback. When he snaps back to real time, Azula has her hands behind her back. When the shot cuts, her hands are instantly by her side.
Continuity mistake: In the shot after Mai says "Saving the jerk who dumped me" you can see the rods which the prison guards used to slow down the mechanism of the gondola are nowhere near the wheel. (00:19:55)
Continuity mistake: When Azula says: "What is she doing?" Ty Lee is standing behind her. When the shot cuts and Ty Lee shrugs, they are standing side by side,. (00:20:30)
Other mistake: When Azula attacks The Western Air Temple, there is a close up shot of her when she says that she is about to become an only child. Pay attention to the smoke coming from the airship behind her, especially above her head: it doesn't move. Even if this was remotely possible, it does move when the camera zooms out, making it a mistake nonetheless.
Audio problem: At the end of this episode, Aang tells Katara that forgiveness is the first step you need to begin healing. But if you watch closely, his mouth isn't moving at all when he says this.
The Ember Island Players - S3-E17
Other mistake: When they are watching the recap play Toph says she can't see it because they are on a balcony, but when her character comes on she describes him as buff.
Sozin's Comet (1): The Phoenix King - S3-E18
Continuity mistake: When Aang is waking up on the giant lion turtle, he is not wearing shoes in the first shot, but in the next shot, he is.
Sozin's Comet (4): Avatar Aang - S3-E21
Continuity mistake: Throughout the entire show, Aang's eyes are grey, but in the last three episodes (Sozin's Comet Part 2, 3 and 4) they are suddenly brown.
Chosen answer: Toph had Katara use it to send a letter to her parents. It never returned.