This was the only one I got, so no need to apologize.
1. Sokka, who is a Muggle, and only occasionally jealous of his sister’s awesome magic skills, is a total NERD. He plans to get a degree in engineering, and his ultimate goal is to have a job where he can blow things up. His mad demolitions skills will be very useful in the fight against Azula. He is also really enthusiastic about Blackadder and Monty Python.
2. Ever since Azula found out that she’s Voldemort’s daughter, she has done her best to make lemonade out of lemons. She has been seeking out the old supporters of her father and courting them. She is not a particular believer in blood purity, but she does believe in a natural aristocracy and an inborn right to rule, something very attractive to Voldemort’s old supporters, who of course imagine themselves as that aristocracy.
3. Azula’s attempts to ingratiate herself with the pureblood supremacists who supported her father makes things very uncomfortable for muggleborn Ty Le, who is having a hard enough time in Slytherin, and as Azula’s minion and abuse victim. It also disgusts Mai, who is sick of hearing that rhetoric from her family, and resents her deeply for her treatment of herself and Ty Lee.
4. Jet is two years older than Zuko, Azula, and the rest, and was old enough to remember his parents dying in the Ministry purges. He has never liked Zuko and Azula, and in some sense viewed them, as Bellatrix’s children, as personally responsible for their mother’s crimes. This only grew worse when he finds out the twins are Voldemort’s children.
5. Toph likes to make a really bright flash of light before charging into battle, to leave her opponents disoriented and induce temporary blindness. Zuko, Aang, and Katara have developed the really bad habit of running into battle with their eyes closed because of this.