Stan could be a likely hero. He's often the voice of reason in the show. He would probably be the one to come up with a practical plan to survive the zombie apocalypse, like finding a secure place to hide and stockpile supplies. He also has a strong moral compass which would help him make decisions about whether to help other survivors or not.
Kenny might be a hero in his own right. Since he has the unique ability to come back to life, he could be used as a sort of guinea pig to test different ways to defeat the zombies. He could sacrifice himself multiple times to gain knowledge about the zombies' weaknesses. And his rough upbringing might give him an edge in the harsh zombie - infested world.
Harry Potter himself would be a likely hero. He has already faced Voldemort and numerous other dark threats, so he has the courage and experience. His ability to think on his feet and his connection to the powerful Patronus charm could be very useful against the zombies.
Definitely Harry Potter himself. He has faced so many dark and dangerous things already, so he'd be able to handle zombies. Hermione would also be a likely survivor. Her vast knowledge of magic and quick thinking would serve her well. And Neville Longbottom. He has shown great courage and has a deep understanding of Herbology, which could be useful in creating defenses or finding antidotes.
Well, Kyle could be a strong contender. He's intelligent and has a strong sense of justice. He'd be able to strategize well and form good alliances. However, his temper might get in the way at times. Another possibility is Stan. He's fairly resourceful and has a good heart, which could help him gain allies, but he might be too hesitant to make tough decisions sometimes.
The members of Team JNPR could also be likely survivors. Jaune has grown a lot in his skills. His leadership and swordsmanship could be useful. Pyrrha, if she were still alive in this fanfic scenario, would be a great asset with her combat abilities. Ren's calm and collected nature, along with his stealth and combat skills, would help him survive. And Nora, as mentioned before, would be a great addition to the group of survivors. They could work together with Team RWBY to face the zombie apocalypse.
Obviously, Stan, Kyle, Cartman and Kenny are the most likely. They're always at the center of the action in South Park. Their different personalities would lead to really interesting time - travel scenarios. Stan's more level - headed nature might be the voice of reason during time - travel chaos. Cartman would probably be trying to use time travel to his own greedy advantage, like finding a way to hoard all the cheesepuffs in history.
One idea could be that the kids of South Park form their own survival squad. Cartman might try to hoard all the food, leading to comical in - squad conflicts. Another could be that the zombies are actually the result of a failed experiment by Professor Chaos, and the boys have to find a way to reverse it. Maybe Stan and Kyle have different ideas on how to deal with the zombie threat, with Stan being more practical and Kyle more idealistic.
Jude could be a likely hero. He's always been kind of a risk - taker and he might be brave enough to face the zombies head - on. His quick - thinking could help the group get out of tight situations.
Lex Luthor. He's always looking for a way to take down Superman, and an apocalypse would be the perfect time for him to make his move. He could be using the chaos to build some sort of doomsday device or manipulate events to his advantage.
I think Naruto and Hiro would be likely to team up. Naruto has his strong will and determination, and Hiro is really smart. Together, they could come up with great strategies in battles. Hiro could use his tech knowledge to enhance Naruto's abilities, and Naruto could teach Hiro about the importance of never giving up.
Definitely Todoroki. His ice and fire powers could be used in different ways against Godzilla. He could try to freeze parts of Godzilla to immobilize it or use his fire to counter any heat - based attacks Godzilla might have. Also, Recovery Girl could be involved in an interesting way. After any battles with Godzilla, she would be needed to heal the injured heroes, and she might also come up with some unique medical strategies based on Godzilla's physiology if she could study it.