Impulse
Bart will be pulled from one of DC's many, many canon AUs. He'll be from the short "My Gun is (Super) Quick" out of their 80 page giant special...yes, that's the actual title. I can upload it if people want!
This world is a black and white (literally) homage to detective classics like The Maltese Falcon. Bart is a renowned private investigator, with his helpful (read: she does all the work) secretary, Cassie Sandsmark. He's largely oblivious to clues (or any femme fatale throwing themselves at him) but gets around by his superspeed whenever he runs into trouble.
While it seems he should be a hard boiled detective, Bart keeps his personality intact. He's still an ADD-riddled kid with a good heart and a tenuous grasp on reality. The only difference is that he might digress into Hammett-esque inner monologue and he's a little older. A nice suit and tie will do that for you. I expect the rest of the DC cast will be busy playing with their own wacky versions so it won't stick out that much.
Mytho will be the same! I briefly thought of Drosselmyer writing "The Prince and the Raven" as a Harlequin romance novel then threw up in my mouth repeatedly.
Azula
Azula will be from an AU where everything was exactly the same except she was born sickly and asthmatic. In fact, her breathing problems kept her indoors or susceptible to illness most of her early childhood. Having another "failure" as an heir, Ozai washed his hands of her and left her to Ursa. She grew up sheltered from a lot of Fire Nation politics with Zuko as a derpy older brother, who spent most of his free time being so excited that she paid attention to him. There were many years of fail!Firesib bonding moments, which redefined how Azula saw the world in some ways.
Apart from that, most of the history is the same. Azula was sent to the Fire Academy and met Mai and Ty Lee. Zuko was exiled for speaking out in the war council. Ozai, realizing she might actually be useful with her improvement in those three years, sends Azula out to collect her brother and uncle. While not a lightning wielding prodigy, she's finally reached a level where master firebenders would find impressive. Season two antics ensue, and they end up in Ba Sing Se, where Azula's plan is just about to come to fruition and all she needs is Zuko to confirm he's on her side.
Personality-wise, Azula is still a manipulative asshole. She's just manipulative in different ways and isn't as direct about intimidation/fear. She believes the Fire Nation is in the right and would cheerfully set the Avatar on fire if she could! The only significant difference is that she's more accepting of how she wants other people to love/approve/pay attention to her. And due to the unfortunate circumstances of being related, Zuko is definitely one of them.
Ramona will be her usual self! The movie is basically just her minus all the background and motivations anyway so pbbbt to that.
...is it sad I'm excited for this just for new icons?