Perhaps there are some superstitious townspeople who see the baby as a bad omen because of its strange origin. They might try to drive Waverly and Nicole out of town, creating a lot of conflict for the two main characters as they protect their baby.
It could be an evil organization that wants the baby for some nefarious reasons. Maybe they think the baby has a special ability that they can use to gain power.
A jealous ex - lover of either Waverly or Nicole might be an antagonist. They could try to create problems for the couple as they are raising the baby together, out of spite or envy.
One idea could be that Waverly and Nicole find an abandoned baby and decide to take care of it together. They face challenges like learning how to be parents suddenly and dealing with the reactions of their friends and family.
The kiss could be a sign of their growing love and connection. It might mark a turning point in their relationship, from just friends or colleagues to something more romantic.
It could be some of the old enemies from the Sailor Moon series who see the baby as a threat. Maybe the Death Busters, if they were still around, would want to use the baby's power for their own dark purposes.
A group of mischievous animals could also be antagonists. They might be jealous of the attention the baby gets from all the other animals in the neighborhood. So, they start playing pranks on Alvin and Brittany, like stealing the baby's toys or making a mess in their yard. But in the end, they could learn to accept the baby and become friends.
Rittenhouse could be antagonists. They might see the baby as a tool or a threat to their plans for controlling time. They could try to kidnap the baby to use its potential powers for their own evil purposes.
It could be Orochimaru. He might be interested in the baby's unique genetic makeup, thinking he can use it to create more powerful experiments. He has always been obsessed with power and the baby's combination of Naruto and Temari's abilities would be very appealing to him.
The Originals' enemies, like the werewolves, could be antagonists. They might see the baby as a symbol of the vampires' growth and power and try to harm it. Also, some of the other vampire factions who are against the Mikaelsons could target the baby to get back at Elijah and Katherine.
There could be a mysterious dark - type Pokémon that is attracted to the unique energy of the baby. It constantly tries to get close to the baby, which poses a threat to the baby's safety. Ash and Cynthia have to fight this Pokémon off while also trying to figure out why it is so interested in their baby.
Demons might also be antagonists. They sense the new life which has a connection to powerful shadowhunters like Jem and Tessa and see it as an opportunity to strike at the shadowhunter community. They could try to possess the baby or harm it in some way.
Maybe some of the old foes from their past could resurface as antagonists. For example, those who were against Marius and Cosette being together in the first place might see the new baby as a way to cause trouble. They could try to spread rumors or create difficulties for the new family.