One common theme is the exploration of Allen's inner struggle. In D Gray - Man, Allen has his own demons to fight, and in mind - control fanfics, this can be intensified. Another theme could be the power dynamics. With mind control involved, the relationship between characters in terms of who has power over whom changes drastically. Also, redemption might be a theme. Allen might be forced to do things against his will due to mind control, and then the story could focus on his journey to redeem himself from those actions.
Well, mind control throws Allen into a state of chaos. His character development is stunted in a sense as he loses control over his actions. But on the other hand, it can also be a catalyst for growth. As he struggles against the mind control, he may develop a deeper understanding of himself. He might realize the true extent of his willpower and the importance of his beliefs. It can also change how he views the world around him. If he's made to do bad things, he may become more empathetic towards those who have been forced into evil, which is a big step in his character development.
Isolation is also a theme. Allen is often alone in his struggles, being the host of the 14th Noah. Fanfics may depict his feelings of isolation from both the Exorcist side and the Noah side, and how he copes with being different from everyone else.
In D Gray - Man Allen and Mana fanfic, the theme of protection is quite common. Mana was like a father figure to Allen, and so fanfics often show Allen's determination to protect Mana's memory or things related to Mana. Additionally, the theme of sacrifice is also present. Mana sacrificed a lot for Allen, and in fanfics, this can be explored further, either from Mana's perspective before his sacrifice or from Allen's perspective as he tries to live up to what Mana did for him.
One common theme is his struggle with his identity. Since he has this complex connection to the Noah, many fanfics explore how he deals with that part of himself.
There are themes like identity. Allen has a unique identity as an exorcist and as someone with a special connection to the Innocence. Fanfictions often explore how this identity affects his decisions and relationships. Additionally, the theme of good versus evil is also common, with Allen being right in the middle of this battle in the D.Gray - Man universe.
One common theme is friendship. Allen and Lenalee's friendship is a central part of many fanfictions. Their loyalty to each other and how they support one another through difficult times is often explored.
A common theme is friendship. Their friendship is often explored more deeply, like how they support each other through tough times in the Order.
One common theme is the exploration of their complex relationship. Given their different allegiances in the original story, fanfictions often delve into how they might interact outside of the main plot's conflicts.
Self - discovery is another theme. Allen is a complex character, and in chibi fanfiction, his journey to understand himself better, his powers, and his place in the world can be told in a really engaging way. It could involve him learning about his past or dealing with his inner demons in a more child - like and endearing manner.
One common theme is the exploration of their pasts. Both Allen and Kanda have troubled pasts that can be delved into in fanfiction. Another theme is their growth as characters, especially in relation to each other. For example, how they overcome their differences and become better comrades.