The villains in the Iron Man universe, like Obadiah Stane (if he were still around), might be enraged. They would see the fanfiction as glorifying Iron Man, and it would go against their own views of him. They might try to find ways to discredit the fanfiction or the ideas it presents.
If it's characters like Rhodey, he might be a bit critical. He knows Tony so well in real life, so he might nitpick the inaccuracies in the fanfiction. But at the same time, he could also enjoy seeing new and exciting storylines that still capture the essence of Iron Man.
Some of them might be critical. Captain America, being a traditionalist, could have issues with how the fanfiction might deviate from the 'true' version of Iron Man he knows. He might think some characterizations are inaccurate. Hulk, on the other hand, might not care much at first, but if the fanfiction angers him in some way, like making Iron Man look bad when he shouldn't, he could get a bit riled up.
Some might be amazed. For example, Hawkeye would be impressed by Iron Man's new flying maneuvers. Others like Falcon could be taking mental notes on Iron Man's technology for his own gear. And Tony Stark himself would probably be enjoying the attention and bragging a bit about his new suit's features.
They might be quite surprised. Some might find it interesting to see how fans imagine different scenarios for Iron Man 3. For example, Thor could be amused by the creative interpretations of Stark's technology. Captain America might be a bit taken aback by some of the more out - there plot ideas in the fanfiction.
The Avengers' reactions would be diverse. Natasha Romanoff might be interested in the character dynamics shown in the fanfiction. She could analyze how the relationships between the characters are different from what she knows in real life. Bruce Banner would likely be cautious. He might worry that some of the fanfiction could mislead the public about the Hulk's nature. And Clint Barton would probably just laugh it off as a fun, fictional take on their lives, but also be a bit critical if it doesn't stay true to their essence as a team.
Well, Captain America might be a bit shocked at first. He's from a different era and fanfiction's modern concept could be strange to him. Thor would probably find it amusing and might even think it's some sort of Midgardian magic story about his friend Stark. Black Widow would analyze it carefully, looking for any insights it might give into Iron Man's character or the public's perception of him.
Well, it depends on the characters. Some might be amused by the creative twists in the fanfiction. For example, if it's a character who is friends with Iron Man in the original story, they might find it interesting to see how the fanfic writer portrays their relationship in a different way.
Some characters might be amused. They could find the creative interpretations in the fanfiction interesting, especially if it gives a new spin on their relationships or adventures in the Batman universe.
Some might be amused. For example, characters like Nagito Komaeda could find the different interpretations of himself in fanfiction either interesting or in line with his self - deprecating view. He might chuckle at how fans perceive his luck cycle in strange new ways.
They might be amused. Tony Stark himself would probably be quite smug, seeing all the creative ideas fans have about him. Steve Rogers might be a bit confused at first by some of the more out - there concepts in the fanfiction. Natasha Romanoff would likely be quietly observant, picking up on the different characterizations of Iron Man in the stories.
They could also be offended. If the fanfiction portrays them in a way that goes against their values or character traits in the original work, they may feel misrepresented. For example, if a character is always shown as noble in the original but is made into a villain in the fanfiction. They might not like this change at all and feel insulted.