Alrighty, although I’m doing this off memory. 2x07 is where all of this information comes from.
Iroh is off fighting in Ba Sing Se, he loses his son Lu Ten in one of the assaults on the wall. Fire Nation family learns off this back home, at the end of a meeting Ozai approaches his father Azulon and basically says ‘Iroh no longer has any heirs, nor is he in any fit state to inherit the throne, please give it to me.’ Azulon gets super pissed and basically as punishment for such insolence orders Ozai to kill Zuko.
Azula overhears all of this and runs to Zuko goading him of the fact daddy is going to kill him. Ursa also finds out what Ozai has been ordered to do (I assume Ozai told her). Ursa then goes to Azulon late at night and kills him to save Zuko. We know this because of her speech to Zuko afterwards and of course at the funeral when they’re like ‘Azulon passed away and as his dying wish wanted Ozai to inherit the throne.’
Lol no, Ursa killed Azulon and Ozai was in on the deal because they conspired to give him the throne. That’s probably the only way Ursa was able to get away with killing Azulon. She was allowed to live because Ozai got what he originally wanted, in return she was able to save Zuko and leave with her life. Simples.
1. The animators think they are well funny and original.

That’s right people. In perhaps one of the most important and climatic scenes of the show where Aang becomes a fully realized Avatar, some overworked and underpaid person though it would be hilarious for the word ‘GAY’ to appear in the receding water.
2. Toph gets in everyone’s pants, no matter the version of ATLA.
A quite well known piece of Avatar trivia, but important none the less. Toph was originally designed as a dude. Her character in Ember Island Players references both her personality and alludes back to her original character plans.

But what a lot of people don’t know is that Toph was also originally a love interest for Katara. Early production notes state that Toph was supposed to complicate the Aang/Katara romance because Katara develops feelings for Toph and Aang gets a bit jealous. But then Toph was switched to a girl and everything changed.

Totally different.
3. Iroh was freed and had weird sexual chemistry with multiple Grand Slam winner Serena Williams.
Remember that nice prison guard who showed compassion towards Iroh?

Voiced by sporting megastar and all round HBIC, Serena Williams.

4. Nickelodeon will never ever learn from their mistakes.
Fool me once, shame on you. Fool me twice, shame on me. Fool me thrice, I’m not sure why some of you still have jobs. Fool me four times, no wait guys, seriously who’s running things up there?

People think Nickelodeon have messed up a few times concerning Korra, what with episodes being uploaded online before they were aired and general sloppiness in terms of spreading information. This is nothing, NOTHING, compared to what happened during Avatar: The Last Airbender.
Episodes were frequently uploaded online before they aired, different countries got episodes ahead of America leading to a massive spoiler fest, DVD’s were released with episodes that hadn’t aired yet and of course perhaps the weirdest fuck up, the release of a graphic novel that gave away the entire finale.

That’s right. This short illustrated book was released WEEKS before the finale (Avatar Aang) was aired on television and gave away everything. At least we got to the Korra finale not knowing Amon was Noatak. This book gave away everything, energybending and final pairings galore. I suppose you can’t really blame Nickelodeon for this, (or can you?) but it does just show the general point of how weird and chaotic it is being an Avatar fan.

(Sidenote: One of my favourite moments as an Avatar fan came when about 1000 posts were made about how this book was a massive fake and that it was just a conspiracy against Zutara fans. To be fair, Katara is dressed wrong and it does seem as if Aang has had a lobotomy.)
5. Iroh’s a really great and inspirational character. Wrong. He’s a massive asshole. Or at least he could have been.
Another gem out of the production notes was the idea that Iroh would be a bit of a dickhead. Instead of joining Zuko on his exile voyage out of the good of his heart and a wish to steer his nephew towards a path of good, Iroh was planning to ruin the fuckers life.

Iroh was originally going to teach Zuko a faulty form of Firebending that would totally ruin any chances of him capturing the Avatar. The idea of Iroh teaching Zuko Firebending made it into the final cut of the show, but of course without the general evillness and family backstabbing.
What a shame, I think if anything, Zuko was really missing a source of angst and despair in his life.

“Your Mother did vicious, treasonous things that night.”
the promise is so much more entertaining when read as an epic gay melodrama

aang doesn’t think he can deal with zuko’s fancy dressing tendencies

but they find a way to get past their differences. the helmet had to go tho.
Fanfiction vs. Reality
I’m just gonna do the main points that really stuck out to me cause no one wants to read a long rambly essay. 
Overall I would say it’s not as bad as I thought it was going to be based on early reviews. But it’s kinda mediocre bordering on tedious. A few moments of brilliance scattered between endless pages of meandering plot.

Zuko is still alive! The next three locations are unlocked for the Republic City game!

SYNOPSIS FOR PART 3:
The Harmony Restoration Movement has failed, and the four nations are plunged back into war! In the midst of the battle, can Aang and Fire Lord Zuko mend the rift between them, or will Aang be forced to take actions that can’t be undone?
Written by Eisner winner and National Book Award nominee Gene Luen Yang (American Born Chinese) and drawn by Gurihiru (Thor and the Warriors Four), this is the adventure Avatar fans have been craving!
I think this is what people were talking about. I’ve got to say I’m not surprised, I don’t have overwhelming confidence in Gene Yang’s writing and it seems neither does this reviewer.
you know what actually, i’ve never gonna shut up about the race thing in avatar. i don’t care if people don’t like debates and it spoils the ~squee~. this shit has real life implications and this whitewashing attitude is endemic of the larger problem in the media.
how do you think they got away with making all the heroes in avatar movie white? it’s cause some people still believe that because avatar is a fantasy it therefore has no connection to the real world. this is simply, empirically, wrong. the creators have said as much (just pick up the art book), the head writer has said as much and anyone who has even the most basic understanding of various asian cultures can see that avatar is absolutely overflowing with references to them. yes, aang is an air nomad, but his culture is based of tibetan culture and pretending that has no relevance to his character is exactly the kind of opinion that allows hollywood to whitewash these characters.
so if you think that the asian influences in avatar mean absolutely nothing, please just unfollow me so i don’t have put up with your misguided and offensive comments when you reblog my posts.
I think there should be a dance competition in the Avatar world where Aang and Zuko team up to breakdance and then round off their number with a classical interpretation of the dragon dance.