Goku is a prime candidate. His time - traveling adventures in the original series make it easy to imagine him in wrong - time scenarios. For example, getting stuck in the past and having to fight enemies without his full power or knowledge from the future.
Shinji is a very likely character. His complex relationship with his father and his role as the main pilot make him a prime candidate for time travel scenarios. He could go back in time to try and fix things or understand his father better.
Ruby and Goku could be a likely pair. Ruby is young and full of potential, much like Goku was when he started his journey. Goku could be a mentor - like figure to Ruby, teaching her about Ki and new combat techniques. Another pair could be Weiss and Vegeta. Weiss is from a noble family and has a sense of pride, similar to Vegeta. They could have an interesting dynamic where they initially clash due to their strong personalities but then grow to respect each other. Yang and Trunks could also be paired. Yang is a strong and fearless fighter, and Trunks has his own badassery. They could team up in battles and share their experiences of growing up in tough situations.
Goku is very likely. He's the main character in Dragon Ball Z. If there's a second chance scenario, his decisions and actions would have a massive impact on the story. He could use the second chance to protect his loved ones better or to reach an even higher level of power.
Artemis could be involved as well. Her skills as an archer and her family's complex history could lead to some interesting time - travel scenarios. For example, she could travel back in time to discover secrets about her family's past that have an impact on her present - day self and the Young Justice team.
Izuku Midoriya is a likely candidate. His strong sense of justice and his journey to become the greatest hero make him a prime character for time - travel scenarios. He might travel back in time to gain more knowledge or to prevent certain tragedies. Another one could be All Might. His past is full of secrets and his influence on the hero world is huge. Time travel could be used to explore more of his backstory or to change some crucial events in his past.
Naruto is a very likely character. Given his strong will and connection to the Nine - Tails, he would be motivated to time - travel to fix problems related to the Juubi. His ability to make friends and influence people would also play a big role in any time - traveling story.
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.
Homer Simpson is very likely to be involved. He's the main character and his bumbling yet loveable nature can create a lot of comical situations in crossovers. For instance, if it's a crossover with 'The Flintstones', Homer would probably be trying to out - eat Fred Flintstone at the local diner.
Goku is often a very popular character in these fanfictions. His powerful abilities and pure - hearted nature make him a great candidate for time - traveling adventures. He might go back in time to prevent a future disaster or to learn new techniques from his predecessors.
Katsuki Bakugo, with his powerful quirk and complex personality, could be a character in time travel fanfics. He might go back in time to prove himself even more or to change certain interactions he had with other characters in the past.