Well, Loki might initially be confused about what to do with the baby. He could try to find the baby's parents. Maybe he uses his magic to keep the baby safe and warm in the meantime.
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Loki could be surprisingly empathetic. He would see a bit of himself in Peter, perhaps, as someone who has been misunderstood. So he'd try to befriend Peter and give him advice on how to handle the bullies without using violence, like using his intelligence.
The baby could be an alien species that Goku has never encountered before. It might have special powers related to its alien origin, like the ability to control energy in a different way than Goku and his friends.
The baby could be an ordinary human baby that has some sort of latent magical ability that Raven senses. She then decides to protect the baby from the human world that may not understand or accept the baby's potential magic, and also from the magical world that might want to exploit the baby.
The baby could be an orphan from a nearby village that has been attacked. Kagome stumbles upon the baby while on her travels with Inuyasha. Since she has a big heart, she can't just leave the baby there, so she takes it with her.
The baby could be a lost elf child from a different part of the forest. Maybe their family was attacked by some dark force and Thranduil finds them by chance.
The baby could be a half - demon, related to some other important character in the series. Maybe it's the offspring of a character Sesshomaru has some history with.