Definitely Naruto. Even if it's a Team Konohamaru time travel fanfiction, Naruto's presence can add a lot of excitement. He could offer his unique perspective and skills, and his interactions with Konohamaru and the team would be really interesting, especially if they travel to a time when Naruto was younger or not even born yet.
Kakashi is another character that would be exciting to include. His vast knowledge and experience, as well as his Copy Ninja skills, would be useful in any time - travel scenario. He could be a mentor figure to Team Konohamaru during their time - traveling adventures, guiding them through different historical events and battles.
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.
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.
Another common plot is Konohamaru accidentally traveling to a time when the ninja world is on the brink of destruction. He then has to use his skills and knowledge from his own time to try and prevent the catastrophe. This often involves him teaming up with ninjas from that era, some of whom might be initially suspicious of him.
One idea could be that Team Konohamaru travels back to the time of the First Hokage. They could witness the founding of Konoha and get involved in some of the early battles against rival clans. Maybe they help Hashirama in some way and learn valuable lessons about leadership and unity from him.
Jiraiya would be an interesting character. His relationship with Naruto could be explored in a new light if Naruto travels back in time. Jiraiya could teach Naruto different things or Naruto could use his future knowledge to help Jiraiya in his missions.
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.
One interesting Konohamaru time travel fanfiction could be where he travels back to the era of the First Hokage. He could learn the original ninja ways and bring that knowledge back to his own time. It might involve him facing challenges like adapting to the older ninja techniques and different social norms in the past.
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.