In a 'Zuko meets Toph' fanfiction, they might start off on the wrong foot. Zuko's serious and brooding nature could clash with Toph's brash and independent attitude. Maybe they get into a small fight at first, but then gradually come to respect each other as they realize they both have a strong sense of justice. For example, they could team up to take on a group of bandits that are causing trouble in a village.
The meeting could start with a sense of mystery. Itachi might appear out of nowhere in Korra's world. Korra, sensing his strange energy, would be on guard. Itachi would be sizing her up, taking in her appearance and the power he can sense within her. They might exchange a few words, with Itachi's soft - spoken nature contrasting with Korra's more direct way of speaking. As they start to interact more, they would begin to learn about each other's abilities and the worlds they come from.
In a 'Korra meets Aang' fanfiction, a storyline could be that Korra is having trouble with her connection to the past Avatars. Aang then comes to her as a sort of mentor, guiding her through the process of strengthening that connection. They could also face a common enemy that is trying to sever the Avatar's connection to the past altogether, which would force them to fight side by side and use their combined powers and knowledge to overcome the threat.
If Korra meets Aang in fanfiction, they may have a deep conversation about the role of the Avatar. Aang could share his story of how he had to end the Hundred Years War and the toll it took on him. Korra could then talk about her struggles in the modern world with things like industrialization affecting the balance of the elements. This exchange would be really interesting as they compare and contrast their Avatar journeys.
Well, Itachi could teach Korra some stealth and perception techniques. Since he's from a world where ninja skills are crucial, he might show her how to better sense danger. Korra could in return introduce Itachi to the concept of bending and how it can be used not just for combat but also for building and healing. They might also have philosophical discussions. Itachi, with his complex past and views on sacrifice, could share his thoughts with Korra, who is often dealing with moral and ethical decisions in her role as the Avatar.
It could be Toph. She's very headstrong and not easily intimidated. Even though Zuko has his own strong personality, Toph would likely push back against any attempts of his to take charge. For instance, if they were in a situation where they had to make a quick decision on which path to take, Toph would probably just start walking in the direction she thought was right without waiting for Zuko's input.
Well, perhaps Korra could learn some of Aang's early airbending techniques. Since Aang was the first Avatar to master airbending in a long time, he might have some unique knowledge to share.
Since 'lemon' fanfic is inappropriate, we can't really discuss the characteristics in that context. But in general, aang is known for his kind - hearted and adventurous spirit. Toph is strong - willed and independent. In proper fanfic, these traits are often explored in their relationship, like how aang's optimism might contrast with toph's more cynical view at times.
Toph's age in the comics can be a bit ambiguous. Different comic series might portray her at different stages of her life. Generally, though, she's often shown as being in her youth, with her age ranging from around 12 to 20, depending on the context.
The 'lemon' aspect might be a bit hard to come by in a clean way as it often involves inappropriate content. But for normal Korra and Mako fanfictions, you could also try FanFiction.net. Some stories there might show their relationship developing, their adventures together, and how they support each other, which can be really interesting to read.