The fanfic could explore how Bucky feels about Steve's concern. Bucky might be a bit prideful and not want Steve to fuss over him. But Steve's worry comes from a place of deep friendship. As Bucky weighs less, it could create a shift in their dynamic, with Steve taking on more of a caretaker role, which could lead to some interesting conversations and moments of tension between them. For example, Bucky might try to prove he's still strong despite his lower weight, and Steve might have to learn when to back off and let Bucky have his independence.
At first, it might be a bit rocky. Tony, being used to his own space, might feel smothered by Steve and Bucky's over - protectiveness. But as time goes on, he'll start to see their good intentions. Steve's moral compass will inspire Tony to be a better person, and Bucky's loyalty will make Tony feel secure. Eventually, they'll become like a real family, with Tony looking up to Steve as a father figure and seeing Bucky as a cool older brother.
Maybe in the fanfic, Bucky has been through some sort of experiment that affected his metabolism and made him weigh less. Steve, being the protective friend, starts to train with Bucky to build up his strength again. They go through a series of challenges together, both physical and emotional, as they try to get Bucky back to his normal self.
On the other hand, Steve might be more understanding than expected. He knows about Bucky's past traumas and could suspect that something else is at play. So, instead of immediately resisting, he might play along for a while, waiting for the right moment to figure out what's really going on and how to help Bucky.
It could also be strained. There might be some jealousy or differences in opinion on how to handle the situation. For example, one of them might want to be more involved with the girl during the pregnancy while the other feels left out, which could cause some tension between them.
In some fanfics, it might be justified in a complex alternate universe scenario. Maybe Bucky is mind - controlled in a way that's extremely difficult to break, and he's forced to act against Steve. However, this goes against the deep - seated friendship between them in the main canon.
Maybe the physical heaviness is a way to show the physical and emotional strain in their relationship. For instance, if Steve has to constantly rescue Bucky or carry him, it could lead to some resentment or at least some challenges in their bond. But at the same time, it could also be a sign of how much Steve is willing to endure for Bucky, showing the depth of their friendship.
In the fanfiction, Steve leaving Tony for Bucky could also make Tony more guarded in future relationships. He might be less likely to trust people easily, especially those who were close to Steve. And Steve, on the other hand, might be focused on building his relationship with Bucky, leaving little room for any kind of reconciliation with Tony.
Well, it could severely strain their relationship. Tony might feel betrayed and hurt. He could start to question Steve's loyalty. Since Steve is ignoring him for Bucky, Tony might become resentful towards both Steve and Bucky. It could lead to a rift that's hard to mend in the story.
A fanfic about Bucky and Loki's friendship could show them on adventures together. Loki's trickery combined with Bucky's combat skills would make for an exciting duo. Their friendship might also develop through a series of heart - to - heart conversations. Bucky could share his struggles with Loki, like how hard it is for him to reintegrate into society. Loki, in turn, could open up about his feelings of being unloved in Asgard. Through these exchanges, a deep and meaningful friendship could form between them.
The Avengers' reactions would be diverse. Captain Marvel, if she's part of the group, might be very matter - of - fact about it. Rhodey could be a bit bemused. Steve and Bucky, in the meantime, would be dealing with the embarrassment of being caught in what might be a very personal moment. The situation could also lead to some new conversations within the Avengers about personal boundaries and relationships among the team members.