A fun plot could be that a magical creature gets into the shower with them. It's a small, mischievous thing that likes warm water. Natsu tries to catch it while Lucy tries to calm it down, leading to a lot of chaos and laughter.
A plot idea could be that an old enemy from Natsu's past returns and targets Lucy to get to Natsu. Natsu then has to go all out to protect Lucy, and in the process, they both learn more about each other's fears and insecurities. Or perhaps there is a magical competition in which Lucy and Natsu team up, and they face various challenges that test not only their magical abilities but also their friendship and trust in each other.
Well, a plot could involve a new student arriving at Fairy Tail Academy who seems to have a connection to Natsu's past. Lucy gets a bit jealous at first, thinking there's more to it. As they all interact, they end up in a magical competition within the academy where they have to team up to face tough opponents. This not only tests their magical powers but also their friendship and loyalty to each other.
Maybe the guild holds a special event where everyone has to swap roles, and Lucy ends up as a maid. Natsu, being his usual self, follows her around, getting into all sorts of comical situations as he tries to help her with her maid duties. For example, he might accidentally set something on fire while she's trying to clean, and they have to work together to fix it.
A great plot could involve Natsu and Lucy adopting a child with no magic. They would teach the child how to be strong in other ways and how to face challenges without relying on magic. The family could then get involved in a mystery that is related to the child's past. As they dig deeper, they discover secrets that not only help the child understand their origins but also put the whole family in danger. It would be a story about family, love, and facing the unknown.
One idea could be that Natsu and Lucy accidentally end up taking care of a baby dragon. Natsu would be excited to teach it fire - breathing tricks while Lucy would be more focused on keeping it safe and fed. Another plot could involve a magic spell gone wrong that turns them into babies themselves, and they have to figure out how to reverse it while in this state. It could also be a story where they find a lost baby in the forest during one of their quests, and they decide to raise it together, which would show their growth as characters in terms of responsibility.
One idea could be that Natsu and Lucy are paired for a school project that involves exploring the magical history of their high school. Along the way, they discover a hidden room in the school that was once used by powerful mages in the past. This leads them on an adventure to unlock the secrets within and also brings them closer together as friends.
One idea could be that in a post - Dragon Cry adventure, Natsu and Lucy are sent on a mission to a hidden island where ancient dragon magic is said to be sealed. Along the way, they face various obstacles that test their bond, like a powerful sorcerer who tries to split them up. Another plot could involve Natsu losing his dragon slayer powers temporarily, and Lucy having to protect him while they search for a way to restore his powers using the knowledge from the Dragon Cry incident.
One interesting plot idea could be that Natsu, in Lucy's body, has to deal with her Celestial Spirit contracts. He might accidentally summon the wrong spirit or get into trouble because he doesn't fully understand how Lucy usually manages them. Another idea is that Lucy, in Natsu's body, tries to use his Fire Dragon Slayer magic but has a hard time controlling it at first, leading to some comical and chaotic situations around the guild. Also, they could both be on a mission while in each other's bodies and have to rely on their friends' help to complete it without revealing their situation.
One idea could be a story where Lucy discovers a powerful magic that can only be controlled with the combined help of Natsu and Gray. So, they have to put aside their usual rivalries and work together closely. This could lead to some really fun and intense training sessions between them as they try to master this new magic.
Another scenario might be a situation where Natsu accidentally eats some magic - enhancing food that makes his emotions go wild. Lucy has to figure out how to calm him down and in the process, they realize deeper feelings for each other. For example, Natsu might start uncontrollably shooting fire everywhere, and Lucy uses her whip to lead him to a safe place where she can try to reverse the effect.