Love or an unusual form of attraction can also be a theme. Given their differences, it can be fascinating to see how writers develop a relationship between them, whether it's a romantic love, a grudging respect that borders on something more, or an unexpected friendship that defies their typical roles in the DC universe.
One common theme is the clash of personalities. Black Canary is often portrayed as a strong and heroic character, while Mad Hatter has his own eccentric and sometimes villainous ways. Their interactions can lead to themes of conflict and resolution.
One common theme is the exploration of madness. The Mad Hatter is, after all, known for his insanity, and when an OC is introduced, they often have to navigate and understand his world of madness. Another theme is transformation. The OC may be changed by their experiences in Wonderland with the Mad Hatter.
You can try fanfiction websites like Archive of Our Own (AO3). It has a large collection of fanfictions, and you can search for 'Black Canary and Mad Hatter' specifically. There are likely to be various interpretations and storylines there.
One common theme is the idea of finding love in a strange and chaotic world. Wonderland is full of madness, but the Mad Hatter and Alice find a connection within that chaos. Another theme is the acceptance of differences. They are very different characters, yet they fall in love, showing that love can bridge gaps in personality and origin.
One common theme is the Mad Hatter's relationship with other characters, like his unrequited love for a certain character perhaps. Another theme could be his backstory and how it affects his actions in the story. And his struggle with the magic or the strange world he lives in is also often explored.
Fantasy and the exploration of Wonderland are big themes. The Mad Hatter x Reader fanfics often describe the fantastical elements of Wonderland in great detail, from the talking animals to the topsy - turvy landscapes. The relationship between the Reader and the Mad Hatter is also often a central theme. It can be a sweet, romantic relationship, or a more complex, platonic bond. Some fanfics also touch on the theme of mystery, with the Reader trying to uncover the secrets of the Mad Hatter and Wonderland.
Love and friendship are also prevalent themes. Some fanfictions might focus on a romantic relationship between the Mad Hatter and the Cheshire Cat, while others may explore a deep, platonic friendship. Writers often use their relationship to explore different aspects of love, loyalty, and acceptance in a fantastical and unique setting.
A common theme is the exploration of madness. Both the Mad Hatter and the Scarecrow are associated with insanity in different ways, so fanfics often dig deep into how their mental states interact. Another theme could be power struggles, as they both have their own forms of power within the Batman universe.
One common theme could be her struggle with the illness while still trying to fulfill her superhero duties. Another might be the support she gets from her friends and allies during her sickness.
Romance can also be a theme, although it might be a bit less common given their different backgrounds. But in some fanfictions, the authors explore the possibility of a relationship between them. Also, there are fanfictions that focus on family - like relationships, with Black Canary acting as a mother - figure or an older sister - figure to Superboy.
One common theme is their friendship. Writers often explore how these two strong female characters support and rely on each other. Another theme is adventure. They are often depicted going on dangerous missions together, using their unique skills to fight villains.