For starters, Zoro is usually seen as a tough and reliable member of the crew. As a baby, the crew would feel a stronger sense of protectiveness over him. His relationship with Sanji could become less confrontational as Sanji would see him as a helpless baby. With Luffy, they'd have a different kind of bond. Luffy would be excited to have a 'new' crewmate in this baby form of Zoro and would want to include him in all kinds of fun activities on the ship. The female crew members like Nami and Robin would take on a more motherly role, and Zoro would be more reliant on them for basic care, which is a huge change from his independent self.
His relationship with Luffy would become more of a big - brother - little - brother dynamic. Luffy would likely play with baby Zoro a lot. Sanji might be more nurturing towards baby Zoro, which is a big shift from their usual banter. Nami and Robin would probably dote on him more, and Usopp might try to come up with little games for baby Zoro.
Well, perhaps an enemy uses a magic spell to turn Zoro into a baby as a way to weaken the Straw Hat Pirates. At first, the crew is in chaos trying to deal with a baby Zoro. But as time passes, they see that baby Zoro has a pure sense of determination. He still tries to train, albeit in a very clumsy and cute way. And in the end, they go on an adventure to find the antidote to turn him back, with lots of comical and touching moments along the way.
Allura and Lance's relationship would also shift. Allura might be more motherly towards baby Lance. She'd use her elegance and grace to take care of him, perhaps singing Altean lullabies. Coran would be the wise old caretaker, sharing his knowledge about the universe with baby Lance in a simple way. Pidge might see baby Lance as an interesting experiment at first, but would also grow to care for him deeply as she realizes he's still their friend Lance, just in a different form.
His relationships would change drastically. His work colleagues, for example, would notice his different behavior. He might start to work at night and avoid daylight. His relationships with other vampires could also be complex. He could form alliances with some vampires who are more sympathetic to his situation, while others might see him as an outsider. In his social circle, he would become a mystery to those who knew him before, and he would have to find new ways to interact with people.
Her relationships with humans would likely become strained. Humans might be afraid of her now that she's a vampire. Her romantic relationships could also change. If she had a human lover, they might have to reevaluate their relationship. And her friendships with other vampires could shift too, depending on how they view her new status as a turned vampire.
Her relationships with her human friends will surely be affected. They might be scared of her at first, or she might be afraid of hurting them. So she may start to distance herself from them.
When the TMNT turn into dragons, their relationships could shift in various ways. Their usual dynamic of being a team of mutant turtles would be disrupted. Maybe Mikey would be the most excited about their new forms and try to get his brothers to embrace the dragon - like qualities more. Raphael might struggle with the change and become more withdrawn, causing the others to reach out to him more. Their relationships would be a mix of adjusting to the new physical forms and the emotions that come with it.
His relationships with his male friends might become more complicated. Some might be more protective of him as a girl, while others might be confused about their feelings towards him. For example, if he had a rival before, that dynamic could shift completely.
For Frisk, they might see Sans in a new light. Instead of the cool and mysterious Sans they know, he's now a helpless baby. Frisk could become very protective, using their determination to keep baby Sans safe. And the monsters in the Underground would likely be more gentle and patient around baby Sans, changing the overall dynamic of the community.
They would become more united as they have a common responsibility. Zoro would be more in tune with Robin's feelings, and Robin would rely on Zoro more for protection.
Their relationship would become more interdependent. Zoro would likely become more gentle and caring towards Nami, seeing her as the mother of his child. Nami, on the other hand, would rely on Zoro more for protection not just for herself but for the baby as well.