The plot might involve Natsu being lured into a trap by a false Dragonoid. Since he has a strong connection with dragons, the false Dragonoid could trick him into a place where he's trapped. He would then need to figure out how to escape and expose the false Dragonoid for what it really is.
In this fanfiction, perhaps Natsu is trapped inside the body or a dimension related to the Dragonoid. It could be due to some kind of dark magic or an accident. As he is trapped, he discovers new aspects of the Dragonoid's power and has to find a way to harness that power to get out while also dealing with any threats that come his way.
It could be a dark wizard who wants to use Natsu's connection to the Dragonoid for his own evil purposes. This wizard might have set the trap to either steal Natsu's power or to use him as a sacrifice to gain more power related to the Dragonoid.
Well, it could be about Naruto somehow ending up in the Fairy Tail world and meeting Natsu. Maybe they team up to fight a common enemy. Naruto's jutsus and Natsu's dragon slayer magic could combine in interesting ways during battles.
One possible plot could be that Marinette, in an overzealous attempt to get closer to Adrien, creates a 'trap' of sorts. Maybe she arranges for a photoshoot at a location where only she and Adrien are present, under the guise of it being a school project related to fashion. She could have set up the set in a way that Adrien would be impressed by her creativity and they would have an extended period of time to talk and bond.
One possible plot could be that they discover the pregnancy and then face challenges together. Maybe they have to deal with the reactions of their friends in the guild, some being happy and supportive while others might be worried about how it will affect their adventuring lives.
The plot might involve Natsu and Mirajane finding a baby dragon in the form of a human baby. Since Natsu has a connection with dragons, he feels a special bond. Mirajane, with her kind heart, steps in to help raise it. They face challenges like protecting the baby from dark guilds who might want to use the baby's power.
One plot idea could be that Natsu has to deal with the physical and emotional changes of pregnancy while still trying to be part of his usual adventures. Maybe his friends are super protective of him now.
Well, perhaps Natsu could be turned into a vampire during a battle with a powerful dark magic user. Then he'd struggle with his newfound vampiric instincts, like the urge to drink blood, while still trying to be true to his friends and his guild.
Well, perhaps Zeref kidnaps Natsu because he sees Natsu as a key to some grand plan. Maybe he wants to use Natsu's power for his own dark purposes. For example, Zeref might think Natsu's unique magic can help him break some sort of ancient curse or gain access to a powerful magic source.
Maybe they are in a dangerous situation and Natsu saves Wendy. In the heat of the moment, they share a kiss out of relief and a new - found closeness.
In a 'natsu married oc fanfiction', perhaps the OC is a healer. Natsu gets seriously injured during a battle and the OC nurses him back to health. Natsu is so grateful and impressed by her kindness and skill that he starts to develop feelings for her. They get married and the story could focus on how Natsu has to adjust to having a partner who is more calm and collected compared to his fiery self. He might learn to be more patient and she might learn to be more adventurous from him.