It could be that the baby is an alien baby who crash - lands on a planet where the beast is the dominant species. The beast might be a huge, furry mammal - like creature.
Maybe the baby is a magical being in a baby form, and the beast is a cursed prince who has been turned into a terrifying beast. Their interaction and the way they help each other break curses could be the focus of the story.
Well, obviously, baby Beast Boy is a main character. The other Titans like Robin, Starfire, Cyborg, and Raven often appear as well. They play important roles in taking care of baby Beast Boy or helping him with his powers.
It could be Trigon. Since Raven has a connection to him, he might see the baby as a way to get revenge on Raven or as a powerful tool for his evil plans. He could try to corrupt the baby's powers for his own use.
The main characters would obviously be the five Avengers. It could be Iron Man, Captain America, Thor, Black Widow, and Hulk. And of course, the baby would be a central character as well. Maybe the story could focus on how each of the Avengers interacts with the baby differently. For example, Iron Man might use his technology to create baby - friendly gadgets, while Thor might tell the baby stories of Asgard.
Obviously, Sonic himself would be a main character, even in his baby form. His friends like Tails, Knuckles, and Amy would also be main characters. Tails could be the one trying to figure out how to turn Sonic back. Knuckles could be the protector, and Amy could be the caretaker.
Obviously, Voldemort as a baby would be one of the main characters. Harry Potter could also be a main character as he has a long - standing enmity with Voldemort. He might be involved in deciding the fate of the baby - voldemort. Dumbledore would surely play a major role. His wisdom would be needed to deal with this strange situation. And Hermione, with her vast knowledge of magic, could be involved in trying to find a way to either reverse the transformation or ensure that the baby Voldemort grows up to be good.
Obviously, Ash would be a main character even in his baby form. Pikachu is bound to be a key character as well, being Ash's closest Pokémon partner. His other Pokémon like Bulbasaur, Charmander, and Squirtle could also play important roles in protecting and taking care of baby Ash.
Obviously, Nightwing himself, even as a baby, would be a main character. His friends in the Bat - family like Batman, Robin, and Oracle would also be main characters. They would be the ones dealing with the situation of baby Nightwing.
Edward, of course, would be one of the main characters. And there could be a female character, like Isabella, who might be Edward's love interest and the potential mother of his baby. Maybe there's also Edward's best friend, Jacob, who gives him advice on this journey of wanting a baby.
The prince would surely be one of the main characters. After all, he is Cinderella's husband and the father of the baby. He would play a crucial role in the story, such as providing support to Cinderella during the pregnancy and helping to raise the child.
Hiccup could be a main character. Since he is Toothless's close friend, he could help Toothless take care of the baby. He might use his human knowledge to build a safe place for the baby to live.