Well, in this fanfiction, it could be that Spiderman uses his agility and web - slinging skills to outmaneuver the enemy. Maybe he creates a huge web shield to protect the Avengers from a powerful blast. His spider - sense could also alert him to hidden dangers that the Avengers might not notice, allowing him to save them at the crucial moment.
A possible plot twist could be that Spiderman is actually from an alternate dimension where he has different powers. And these powers are the key to saving the Avengers. For example, he might be able to time - travel in this dimension and go back to prevent the event that put the Avengers in danger in the first place.
Perhaps the Avengers are under some sort of mind - control spell. Spiderman, being immune to the spell for some reason, has to figure out how to break it. He might swing around, avoiding attacks from his brainwashed friends, and then find a way to disrupt the source of the mind - control. For example, he could web up a device that was emitting the mind - controlling waves.
Perhaps it could be a character from an alternate dimension. In some fanfiction scenarios, portals open between different dimensions, and Spiderman could have had an encounter with a female character from another world, which led to the baby.
One possible plot could be that Naruto is on a mission in a village when he hears a baby crying. The baby is in danger because a group of bandits is about to raid the house where the baby is. Naruto quickly uses his ninja skills to fend off the bandits. He then takes the baby to a safe place, like the local hospital or an orphanage. Along the way, he might have some cute interactions with the baby, like making the baby laugh with his shadow clone jutsu.
Well, the plot could be that the baby is in a high - rise building that's on fire. Spiderman swings in, using his web to create a sort of cradle to catch the baby as it's being passed out of a window by a desperate mother. Then he safely descends the building with the baby in his arms and hands it over to the paramedics waiting below.
Well, perhaps in the fanfiction, Spiderman saves a woman who later turns out to be pregnant with his child. He doesn't know about it until she shows up at his doorstep with the baby. Spiderman then has to figure out how to take care of the baby. He might start using his web - slinging skills in new ways, like creating a safe web - hammock for the baby to sleep in while he's on patrol, and he has to deal with the reactions of his friends and allies, like Mary Jane or Ned.
Well, in a fanfiction, it could be due to some sort of magic spell gone wrong. Maybe a villain was trying to defeat Spiderman in a new and unique way and accidentally turned him into a baby. Another possibility is that some strange scientific experiment in the Marvel universe backfired on him.
His identity might be at risk. If people find out that Spiderman has turned into a baby, it could expose his secret identity. Also, his friends and family would have to take on new roles. For example, Aunt May would have to be more of a caretaker than ever, and his superhero friends would need to protect him from villains who might see this as an opportunity to get rid of Spiderman once and for all.
One common theme is sacrifice. Sirius is often willing to put his own life on the line to save Harry. For example, in many fics, he battles powerful dark forces without hesitation to protect the baby.