Another theme is the exploration of their different personalities. Arthur is usually more responsible and DW can be more carefree. Fanfictions play with this by putting them in situations where their personalities clash at first but then they find a way to complement each other. For instance, in a story where they are planning a party for their parents, their different approaches initially cause problems but in the end lead to a great celebration.
Since 'arthur dw tantrum fanfic' is not a very common or widely known term, it's difficult to say precisely. However, generally in fanfics, when we have something like this, it could be a story where the focus is on Arthur and DW having a fit or a tantrum. This could be due to various reasons like not getting what they want, facing a difficult situation at home or school in the Arthur - related world. The fanfic might then detail how they express their anger, and how others around them respond to these outbursts.
One great 'arthur x dw arthur fanfiction' could be 'Arthur and DW's Unlikely Adventure'. It takes the characters on a journey through a magical forest where they have to solve puzzles together. This fic really plays on their unique relationship and the differences in their personalities.
One great 'Arthur and DW fanfic' could be 'Arthur and DW's Adventure in the Magic Forest'. It has a really interesting plot where they go on a journey to find a lost magical creature. The story shows their sibling bond in a new and exciting way.
You could try looking on popular fanfiction websites. Websites like Archive of Our Own (AO3) or FanFiction.net might have it. Just search for 'arthur dw tantrum' on their search bars.
One popular theme is their sibling rivalry. Many fanfics explore how Arthur and DW compete with each other, like for their parents' attention or for the best toy. It makes for some really engaging stories as they try to outdo each other in different ways.
Since we have no details about the story, it could be a legend passed down in Atlantis. Maybe it's a story about a great hero from their past, and Mera is telling Arthur this story to inspire him or to give him some historical context that could be relevant to their current situation. It could also be a story about the magic or unique powers that exist in their world, which Arthur may need to understand better for some future task or challenge.