Gwen could be an interesting addition. Her magic powers could interact in unique ways with the time - travel concept. Maybe she could use her magic to repair time rifts that Ben accidentally creates during his travels. Also, she could provide a different perspective on the events they encounter in different times.
Vilgax would be a great character. If he gets hold of time - travel technology, he could try to rewrite history to make himself the ruler of the universe from the very beginning. Ben would then have to race against time to stop Vilgax from changing the past and destroying the future as he knows it. This would create a lot of tension and action in the fanfiction.
Definitely Ben himself. His ability to transform into different aliens makes for interesting scenarios in different time periods. For example, in the past, he could transform into an alien that was thought to be a myth, causing all kinds of chaos or amazement.
Gwen could be really interesting. She could have developed different powers in a different time period that Ben discovers when he travels back. Also, Grandpa Max in his younger days would be cool. He might have been involved in some secret time - traveling adventures that Ben uncovers. And Vilgax from different points in time could add a lot of drama. Maybe a younger Vilgax who is still learning and more vulnerable, or an older, more powerful Vilgax from a far - off future.
Morgan could be an interesting addition. He might accidentally get caught up in Chuck's time - travel adventures. His comical nature could provide some light - hearted moments in an otherwise complex time - travel plot, like when he misunderstands the technology or customs of a different time.
Issei himself is of course very interesting. His reactions to different time periods and how he uses his knowledge from the future can be really engaging. Then there's Rias. Her presence can add a layer of complexity, especially if she has different relationships with Issei in different timelines. Another interesting character could be Vali. His rivalry with Issei can take on new dimensions when time travel is involved, like competing in different historical battles or for the affections of a character in a different era.
One idea could be Ben going back in time to prevent an alien invasion that in the original timeline led to the destruction of his hometown. He could use his ultimate alien forms in creative ways to outwit the invaders before they even start their attack.
Ben Tennyson is definitely an interesting character to include. His ability to transform into different aliens gives a lot of possibilities for the story. Finn the Human is also great. His adventurous spirit and his sword - fighting skills can add action to the fanfiction. Jake the Dog can be really fun too, with his shape - shifting abilities. And of course, Princess Bubblegum, her intelligence and leadership can bring a different dynamic to the story.
Rick is an obvious choice. His intelligence and knowledge of the multiverse can add a lot of depth to the time travel story. He could be the one helping Morty fix the problems caused by time travel, or he could be the cause of the problems in the first place. Another interesting character is Summer. She could get involved in Morty's time travel adventures, and her different perspective as Morty's sister can bring new elements to the story. Maybe she's jealous of Morty's time - traveling and tries to tag along.
One of the most interesting characters to include would be Orochimaru. His thirst for knowledge and immortality could lead to some really wild plot twists in a future time - travel fanfiction. Then there's Shikamaru. His intelligence could be used to strategize in a future full of new challenges. And Sakura. Her growth as a ninja and her relationship with Naruto and the others could bring a lot of depth to the story.
One character that would be fascinating is Medivh. As a powerful mage with knowledge of time and magic, he could either be a helper or a hindrance to Anduin. He might know secrets about the time travel that Anduin is doing and use it to his own ends. Another interesting addition could be Illidan Stormrage. His complex relationship with power and his own past actions could make for some intense interactions with Anduin as he travels through time.
Fugaku himself is obviously a very interesting character. His journey through time allows us to see different sides of him. He might be a strict and stoic clan leader in his original time, but during time travel, we can see his vulnerability and his struggle to adapt to different situations. Another interesting character could be his younger self. The interactions between Fugaku from different time periods can be really fascinating, as he tries to guide or understand his younger self. Also, any characters who are aware of the time travel and try to manipulate it for their own gain, like a rogue ninja who wants to change history to gain power, can add a lot of intrigue to the story.
Goku would be really interesting. His naivete in a time - travel situation could lead to all sorts of unexpected events. He might not fully understand the implications of changing the past and end up doing things just because they seem fun at the moment. Sanzo is also a great choice. His no - nonsense attitude in a different time period could create a lot of conflict, especially if he has to deal with the different cultural and social norms of the past. Another interesting character is Hakkai. His intelligence and ability to adapt would make for some really engaging time - travel stories as he tries to figure out how to use his skills in a new and unfamiliar time.