The glance that Aang, Sokka, and Katara trade with each other just sells it. And it's made more tearjerking if you realize that this confrontation is the only time in the entire episode that either of Toph's parents have even spoken to her directly. As the creators themselves put it, despite Toph's arrogance and toughness, it's kind of sad how she just grew up so lonely.

Toph's confrontation with her parents at the end of her debut episode.

Zuko parts ways with Iroh, after Iroh shows disappointment in him for stealing.

He also off-handily mentions that's it's not surprising he saw Yue because he thinks about her all the time. Even if Yue was a hallucination, it's pretty clear that Sokka blames himself for letting Yue die. Before he had a chance to counter her statement, she disappeared and you can tell that Sokka is very crestfallen. To make it worse, 'Yue' claims that he didn't protect her.

Even though he believes that the swamp isn't magical, he was wondering if he really was seeing Yue.

Avatar the last airbender ostrich horse