One idea could be that the Avengers themselves get injured during a major battle and are taken to a special hospital. There, they have to deal with not only their physical wounds but also the psychological trauma. For example, Iron Man might struggle with the fear of his suit failing again while in recovery. The doctors and nurses in the hospital could be normal humans who are in awe of the Avengers but also have to keep their professional composure.
Maybe the hospital is secretly run by a villain who is using the Avengers' injuries as an opportunity to study their powers. The Avengers start to notice strange things happening around the hospital, like their powers being drained slightly. Hawkeye could be the first to suspect something is wrong as he is very observant. They then have to figure out what's going on and escape the hospital while still injured.
In the fanfiction, the Avengers could be visiting a hospital to see a young fan who is terminally ill. They end up spending time with other sick children as well. Captain America could inspire the kids with his stories of courage. This visit could also lead to the Avengers funding a new wing in the hospital dedicated to treating superhero - related injuries that normal hospitals are not equipped to handle.
One possible plot could be that a character gets seriously injured during a battle and is rushed to the hospital. While in the hospital, they have to deal with their own fears and insecurities as they recover. Meanwhile, their teammates visit them and there are some heart - to - heart conversations that strengthen their bonds.
In this fanfiction, a young medical ninja in training could be struggling to prove herself in the hospital. She has to deal with difficult patients, strict mentors, and the pressure of the constant stream of injured ninjas. One day, a very important and powerful ninja is brought in with a life - threatening injury. This is her chance to shine, but she also has to face her own insecurities and the politics within the hospital.
Perhaps in the fanfiction, the Avengers reunite for a more personal reason. One of their own, say Tony Stark (even if he's no longer alive in the main timeline), has somehow sent a distress signal from an alternate reality. They come together, not just to rescue him but also to explore this new and strange reality where things are different. They might meet alternate versions of themselves and have to team up with these versions to solve a problem that is affecting both realities.
Obviously, the Avengers themselves would be main characters. Iron Man could be the one who funds the high - tech medical equipment in the hospital. Thor might have a hard time adjusting to the human medical procedures. And Black Widow could be using her espionage skills to find out if there are any threats in the hospital.
One possible plot could be that Snape is injured during a battle against dark wizards. He ends up in the hospital wing at Hogwarts. While there, students who once feared him start to see a different side of him as he is vulnerable. Hermione might visit him out of curiosity and they end up having deep conversations about potions and the wizarding world's future.
A different plot could be that Iron Maiden is on a world tour when they accidentally stumble upon an alien technology that the Avengers are also after. This technology is the key to stopping an impending alien invasion. The two groups then have to work together, with Iron Maiden bringing their creative thinking and the Avengers their combat skills, to figure out how to use the technology and save the world.
One possible plot could be that Oliver Queen gets transported to the Avengers' universe. He teams up with Hawkeye, sharing their archery skills and combat tactics. They could go on a mission to stop a new threat that combines the technology of the Arrowverse and the super - powered enemies of the Avengers.
One interesting plot could be Spider - Man having to prove himself to the Avengers. Maybe he starts as an outsider, but through his unique skills like web - slinging and his spider - sense, he helps the Avengers in a mission that they initially thought was impossible. For example, infiltrating a high - security enemy base that is full of high - tech traps.
A cool plot might be that the Tailed Beasts in the Naruto world are being targeted by an unknown force from the Marvel universe. The Avengers, thinking it could lead to a greater threat to both universes, come to help. Naruto and the Avengers have to work together to protect the Tailed Beasts. Hulk could have an interesting interaction with the Tailed Beasts, perhaps learning from them how to better control his rage, while the ninjas are amazed by Thor's lightning powers and try to incorporate some of that into their own jutsu.
In the 'Avengers and Loki Christmas fanfiction', it could be that an ancient Christmas - themed evil force is awakened. The Avengers are initially baffled on how to deal with it as it uses Christmas magic in a malicious way. Loki, having knowledge of both magic and trickery, offers his help. Together, they go on a journey to find the source of this evil. Along the way, Loki and the Avengers have many arguments and moments of understanding. By Christmas Eve, they manage to defeat the evil force, and Loki stays with the Avengers to celebrate a well - earned Christmas, having become a sort of honorary Avenger for the time being.