One idea could be that Tikki and Plagg get accidentally switched with two other kwamis for a day. This would lead to chaos as Ladybug and Chat Noir have to deal with the different powers and personalities of the new kwamis. Another plot could be that Tikki and Plagg discover an ancient secret about their origin that could change the way they view their roles as kwamis. Maybe they find out they were created for a purpose other than just powering the Miraculous.
Tikki and Plagg might interact by sharing stories about their past experiences with different holders. For example, Tikki could tell Plagg about a very brave Ladybug from centuries ago, and Plagg could share his tales of mischievous Chat Noirs. They could also argue about food, with Tikki preferring sweet things like cookies and Plagg loving stinky cheese.
Honestly, it's hard to pick the 'best' writers as there are so many talented ones. However, [writer's name 3] has written some really unique fanfictions. They explore the more philosophical aspects of Tikki and Plagg's existence. And then there's [writer's name 4] who is great at writing humorous fanfictions about the two kwamis. Their dialogues are always on point and make the stories really enjoyable.
One popular theme is the relationship between Tikki and Plagg. They are polar opposites, Tikki being the kwami of creation and Plagg of destruction, and exploring how they interact in different situations can be really interesting. Another theme could be the adventures they have with their holders. For example, when their holders face tough villains, how Tikki and Plagg guide and assist them. Also, stories about their origin and the history of the Miraculous they are associated with are quite popular in fanfiction.
One possible fanfiction could be about Marinette's daily life with Tikki. For example, Marinette could be having a tough day at school, getting bullied by Chloe. Tikki, being her kwami, tries to cheer her up by suggesting they make some special macarons. They then spend the evening in Marinette's room, sharing stories and laughing, which helps Marinette forget about her bad day.
One adventure could be that they accidentally get separated from their holders and have to find their way back. Tikki might use her ability to sense positive emotions to lead the way, while Plagg complains the whole time about being hungry. Along the way, they encounter other kwamis who either help or hinder them.
Well, they could get into all sorts of mischief. Maybe they decide to play a prank on their holders. Tikki could use her positive energy to create an illusion of a delicious macaron that Plagg can't resist, but when he tries to eat it, it disappears. And then Plagg could use his Cataclysm to create little harmless 'disasters' like making a small pile of papers look like they've been completely destroyed, just to make Tikki gasp in surprise.
In this fanfiction, Marinette and Tikki could be transported to an alternate version of Paris. Here, everything is different, and they have to find a way back. Marinette uses her wits and Tikki's knowledge to navigate this strange new world. They meet different versions of their friends and enemies, and through their adventures, they learn more about themselves and their relationship.
Perhaps Plagg cries because he feels guilty. He might have made a mistake, like accidentally revealing something to the wrong person about the Miraculous powers or secrets. This guilt could be overwhelming for him. Also, it could be that he's sad about the state of the world in the Miraculous Ladybug universe. There are so many akumas and problems, and he might feel powerless to really change things in a big way.
First, describe his physical appearance when crying. Say something like 'Plagg's big green eyes were filled with tears, his little body shaking as he sobbed.' Then, show his internal thoughts. For example, 'Plagg thought about how alone he felt, even with his chosen wielder, in this big, dangerous world.'