Dumbledore would probably take it in stride. He has seen many strange things in his long life. He might see it as a chance for Harry to experience a different perspective, and with his twinkling eyes, he would watch the whole situation unfold with amusement and a bit of wisdom, knowing that it's all part of the magical world's unique charm.
Ron might laugh out loud at first. He has a good sense of humor and would find the whole situation hilarious. But then he would also be a bit worried about Harry's dignity. Ginny, on the other hand, would probably blush and giggle. She has a bit of a crush on Harry and seeing him in such an adorable yet silly state would be both endearing and embarrassing for her.
Most of Harry's friends from Hogwarts would be surprised, but they would quickly show their support. Neville, for instance, would be happy for them and might offer to help with any magical plants that could be useful for the baby, like those with calming or protective properties. The other Aurors that Tonks works with would probably be a bit more reserved in their reactions, but they would respect their colleague's decision. And the centaurs in the Forbidden Forest, if they were aware, might see it as a sign of new beginnings in the wizarding world, a new life that could bring balance or change to the magical realm.
Well, it could be a humorous story. Maybe Tonks has some mischievous reason for dressing Harry as a baby. It might be part of a prank within the wizarding world, like she wants to see the reactions of others, especially Harry's friends. For example, Hermione might be shocked at first and then find it quite funny.
Hermione would probably be initially shocked but then would be very curious about the magical properties that might have caused the transformation. Ron, on the other hand, would likely tease Harry at first but would soon come to accept it and see it as just another strange thing in the wizarding world.
Zazu would be flustered. He's used to reporting to the grown - up Simba and giving advice. With Simba as a baby, he would be at a loss for a while. He would try to maintain order in the pride but would also be constantly worried about Simba's safety. The hyenas, if they got wind of this, would see it as a chance to cause chaos. They might try to attack the pride while they think Simba is vulnerable. But the pride, united by their love for Simba (even in his baby form), would be ready to defend their king and their territory.
It might also be part of a mission or a disguise for some reason. In the wizarding world, strange disguises are not unheard of. Tonks, being a Metamorphmagus, decides that dressing Harry as a baby would be the perfect way to sneak him into a place where no one would suspect his true identity.
If Harry went back to when his parents were at Hogwarts, his parents would be really confused at first. But then they would probably feel an instant connection to him. Lily might be very protective right away, while James would be curious and try to figure out how this baby got there.
Temari and Kankuro would probably be very protective. They've always been close to Gaara, and seeing him as a baby would bring out their nurturing sides. They'd do everything they could to keep him safe and find a way to turn him back. Naruto, on the other hand, would be shocked at first but then would see it as his duty to help. He has a strong sense of justice and friendship, and he wouldn't abandon Gaara in such a state.
The Cullens would probably be very protective. They've always been protective of Renesmee, and with the addition of a baby, they would likely do everything they could to keep it safe. Bella and Edward would be overjoyed grandparents, and they'd use their combined knowledge and powers to ensure the baby's well - being. The werewolf pack might be a bit more hesitant at first. Jacob's relationship with the pack has been complex, and a half - vampire, half - werewolf baby would be a new concept for them. But ultimately, they would also come around to protect the baby because of their loyalty to Jacob.
Well, in the fanfiction, if we consider the people around Harry, the teachers at Hogwarts could be concerned at first. Dumbledore, being the wise figure, might see potential in the baby and encourage Harry. As for Edward's friends in the vampire coven, they would have mixed feelings. Rosalie might be jealous as she always wanted a normal life with a baby. Jasper might be worried about the baby's influence on their coven's stability. But overall, as time passes, they would adapt and form a new kind of community around the baby.