Another theme could be danger. The mystery girl might be in some sort of danger or be the cause of danger to others, which adds to the overall intrigue of the story.
Family secrets are also a common theme. For example, in some graphic novels, the mystery girl discovers that her family has a hidden past that she has to uncover. Friendship is another key theme. In 'Lumberjanes', the girls' friendship helps them solve the mysteries they encounter at the camp. And there's often a theme of the unknown or the supernatural, as in 'The Wicked + The Divine' where the gods' presence brings a lot of mystery and the unknown into the story.
Another theme is the solving of a mystery that Rex is either a part of or is somehow related to. This could be a mystery about a lost civilization or a strange phenomenon that only Rex can help solve. For example, in some fanfictions, Rex has a connection to an ancient artifact that holds the key to solving a big mystery. This creates a lot of suspense and adventure in the story.
One possible theme could be the search for identity. Since it's a mystery involving a girl, she might be on a journey to discover who she really is. Another theme could be secrecy. Mysteries often involve secrets that need to be uncovered.
In mystery novels, a common theme is the presence of a mysterious or suspicious character. This character might be the villain or just someone with a hidden agenda. Another theme is the setting which can add to the mystery. For example, a spooky old mansion or a fog - covered alley can enhance the sense of mystery. Additionally, the theme of danger is often there. The characters, especially the protagonist, are usually in some kind of danger as they dig deeper into the mystery. It could be physical danger like being attacked or more of a social danger like having their reputation ruined.
One common theme is the search for truth. The detective or protagonist is constantly trying to figure out what really happened, whether it's a murder, a disappearance, or some other mystery. Another theme is deception. There are often characters who are lying or hiding something, which adds to the mystery. Also, justice is a big theme. Usually, the mystery is solved to bring about some form of justice, whether it's putting a criminal behind bars or clearing an innocent person's name.
One common theme is heroism. The Armor Girl is often depicted as a hero, fighting for justice and protecting the weak. Another theme is self - discovery. She usually goes on a journey where she learns more about herself and her powers. Also, the theme of friendship or comradeship is present as she often teams up with others.
One common theme is self - discovery. When a character turns into a girl, they often have to explore their new identity, understand their new body, and figure out how to fit into society in this new form. For example, they might have to learn new social norms associated with being female.
One common theme is her struggle with her identity. Given her complex origin story, many fanfictions explore how she comes to terms with who she really is. Another theme is her relationships, whether it's romantic relationships or friendships with other superheroes.
Friendship is a very common theme. The relationship between the girl and Toothless is often based on mutual understanding and support.
Power - control is also a common theme. She might struggle with how to use her powers properly or face the consequences of using them in the wrong way. Love and romance can also be a theme, like her having a secret crush on another hero or someone she meets during her adventures.