The main theme could be about acceptance. It shows how a boy with a facial difference is trying to be accepted in the society and also how people around him learn to accept him for who he is.
Well, the main theme might be related to a journey. Since it's called 'the wonder house novel', perhaps the characters are on a journey of exploration within this 'wonder house', which could involve self - discovery, uncovering secrets, and facing various challenges.
Another possible main theme is perseverance. The simple promise gives a goal, and the characters have to persevere to achieve it. In the Mario world, there are many difficulties like bottomless pits, flying enemies, and complex mazes. The characters need to keep going, keep trying, in order to fulfill the promise. So the fanfic could focus on how they don't give up, no matter how tough things get, all because of that one simple promise.
The main theme could be family and the magic of Christmas. It often shows how the family comes together during the Christmas season, sharing traditions and creating memories.
I'm not sure as I haven't read the story. But it could be about discovery or the magic of seeing things from a different perspective, just based on the title.
The fanfic has also led to more discussions within the Mario fandom. Fans debate about the plausibility of the relationships and storylines in the 'bowsette and mario' fanfics. This kind of interaction keeps the fandom alive and engaged, as everyone has their own opinion on how the Mario universe can be expanded or re - imagined.
The main theme is often considered to be about the power of literature. It shows how books can shape lives, hold memories, and have a lasting impact on individuals and society.