This is where I realize that my obsession with tiny, minute details is probably unhealthy. But I will be anal-retentive until the day I die, goddammit!
I've seen Zuko referred to as the "Crown Prince of the Fire Nation" in several fics, despite it being a term I don't remember hearing in the series. Granted, the series is mostly Eastern and the term "Crown Prince/Princess" is a European one. So, I did what I usually do when pondering the unimportant -- I used
Wikipedia.
Anyway, the crown prince of a nation is the heir-apparent. The person who, if the king chokes on a pretzel at dinner, will rule the country by breakfast. So, except for 11 episodes in season three, Zuko is srsly not the crown prince. That title would go to Azula. (And yes, I do mean the title crown prince -- Azula has bigger balls than Zuko, and does not sit in her room crying and listening to Dashboard Confessional. BUT I DIGRESS...)
Granted, the characters may think of Zuko as crown prince after he joins the Gaang. After all, he's a better option as ruler than Azula or Fire Lord Ozai
Luke Skywalker. (Come on, am I the only one who pulled a "Zuko, I AM your father"?!)
So. That's way more information than anyone ever needed to know. Yep. Back to writing!