I have many....but i'll just say two that i truly remember and i came to really like very much....and they have well developed backgrounds too.
sweatdrop First up
Yu-Lin
Age: 10
Occupation: servant of Fire Lord Azulon's palace (this is all before zuko's banishment and s**t...)
story: she's being mentally and physically abused by Azula everyday she works. Zuko notices this one day and offers her his friendship, which she gladly excepts. Since Ty Lee and Mai almost always come to the palace to hang out with Azula, and since she is always torturing poor Yu-Lin in front of them, Ty Lee--being the caring person that she is, offers her companionship to Yu-Lin as well, which she accepts as well. Yu-Lin, Zuko, and Ty Lee quickly become good friends and Ty Lee notices that Zuko and Yu-Lin's relationship becomes increasingly closer over the years. Mai also notices this and, since she's in love with Zuko, she become infuriated and jealous of Yu-Lin and makes her life a living hell along with Azula.
yeah, i know....uber long....and it gets longer. i'm writing a fanfiction about her and it's going to be split into three parts.....
sweatdrop give me a pm if you would like to read it. i would be more than happy to give you the link. ^_^
Next
Rika
age: 15
special ability: waterbender
occupation: teacher's aide to Yagoda (a.k.a. the waterbending healer in episode 1.18 "The Waterbending Master")
story: she's an only child who loves to have reckless fun, but being a woman, and living in the Northern Tribe.....she can't really do that now, can she? The only thing she can do is use her waterbending to help Yagoda teach other women/girl waterbenders to heal. But, she has a friend, Gin, who is learning from Master Pakku how to spar and use his waterbending to fight....so he and Rika go out to a remote location during the night and he teahes her some things that he has learned. They haven't been caught yet so far.....
yeah, i know......my whole reply is GIGANTIC but....i had so much to say about them, that the descriptions took a mind of their own.
sweatdrop haha....
Yu-Lin's story is more developed....and sounds more interesting....to me, anyway.
sweatdrop