He might react with defiance. Teddy is not one to back down easily. If Umbridge tried to impose her unjust rules on him or his friends, he would likely oppose her openly. He could use his ability to change his appearance to make a statement, like turning into a wolf (in honor of his father) to show his strength and resistance.
Well, one possibility is that Teddy, being the son of Remus Lupin, would likely be filled with a sense of justice. He might immediately be on guard around Umbridge. Since Umbridge was known for her cruel and unjust ways at Hogwarts. Teddy could use his Metamorphmagus abilities to play tricks on her, like changing his appearance to something that scares her when she's being particularly mean.
James might be really excited. He's heard stories about his father's friends, and Teddy is like a link to that past. He'd probably be full of questions about the Marauders and what his dad was like as a student. Lily, on the other hand, would be more reserved but still interested. She might be a bit more empathetic towards Teddy, considering his difficult past. Overall, they'd both be curious and eager to learn more from him.
They would probably be horrified. The Dursleys have always despised magic and those associated with it. Teddy, being a young wizard, would represent everything they dislike. They might try to shoo him away or call the police, thinking he's some sort of freak.
It could be one of his professors. If Teddy was constantly late to class or not doing his homework, a strict professor like Professor McGonagall might send a Howler to set him straight.
Hermione might also try to turn the situation around to expose Umbridge's tyranny. She could gather evidence of Umbridge's improper behavior during the punishment process and then use it to convince the other teachers or even the headmaster that Umbridge is a bad influence in the school. This would be in line with her intelligent and problem - solving nature.
One idea could be Teddy exploring his father's memories through a magical object and having conversations with Remus in those memories. It could be a way for Teddy to really understand his father on a deeper level.
She'd probably be horrified. Fanfiction can have all sorts of wild ideas and interpretations that go against her traditional views. For example, if there are relationships in the fanfiction that she doesn't approve of or characterizations that are different from what she thinks is right, she'll be very unhappy.
They are popular because Harry has a connection to Teddy through his father, Remus Lupin. Harry can act as a father figure to Teddy, and this relationship has a lot of potential for emotional depth. It's a way to explore the idea of family and mentorship in the wizarding world.
One possible scenario in this fanfiction could be that Teddy shows some unique magical abilities that remind Remus and Tonks of their own magical heritages. Maybe Teddy can transform in a way that combines both werewolf and metamorphmagus traits, which would be a really interesting plot point. It could also explore how Remus and Tonks, who had such a tragic end in the original story, get to experience some happy moments with their son Teddy through the magic of fanfiction.
It could be Harry Potter himself. He has been a victim of her tyranny and might finally find a way to expose her once and for all.