aang and katara

Azul is Spanish and Portuguese for blue, possibly a reference to Azula's Firebending.
Her name may also come from the Sanskrit term Asura, a Hindu term for demon.
Azula's name was originally going to be "Zula".

In some 阿凡达 comics, her name is mispelled "Takara" instead of "Katara".
Katara's voice actor, Mae Whitman, has previously played the part as Rose in American Dragon: Jake Long.

The Southern Air Temple is the only episode in which the 标题 screen, which denotes the chapter and book, does not have a white background (the background is the sunrise).
According to the Nick.com's website...

Azula hadn’t really considered her appearance in any sort of way at all, much less she hadn’t ever thought herself unattractive.
It never seemed to matter.
Never seemed to come up.
Being a princess, even a solider of sorts, beauty wasn’t something Azula ever thought she’d contemplate.

And yet, the princess found herself standing in front of the mirror wondering what was wrong. She never dwelled on her looks and so she never had the chance to realize that she wasn’t pretty in the slightest. Hadn’t had the chance until now.

The princess rubbed the wetness out of her eyes with the back...