One great fanfiction could be where Sirius Black travels back in time to prevent his own imprisonment in Azkaban. He might use his knowledge of the future to avoid being framed by Peter Pettigrew. This could change the entire course of the story, as Harry would then have a more stable and present godfather figure in his life from an earlier stage.
One great fic could be 'A Time for Changes'. It beautifully weaves the relationship between Harry and Sirius while using time travel in an interesting way. The author creates a believable alternate timeline where their relationship develops in unexpected ways.
In some fanfictions, Sirius Black time travels to the past and teams up with his younger self. They work together to expose the Death Eaters' plans earlier. This creates a really cool dynamic as the older Sirius has more experience and the younger one has more energy and impulsiveness.
Love and sacrifice are also prevalent. Harry and Sirius' relationship deepens in these fics, and they often have to make sacrifices for each other during their time - traveling adventures. For example, Sirius might sacrifice his own safety to protect Harry in a different time era. And the theme of family is important too. They form a sort of family unit that is different from the traditional ones in the wizarding world.
Fanfiction about James Sirius time travel can also play with the concept of destiny. Does time have a set path that cannot be changed, even with time travel? Or can James Sirius rewrite his family's future? These philosophical questions add depth to the stories and keep readers engaged as they ponder along with the character.
One great fanfiction could be where Hermione travels back in time to save Sirius. Maybe she uses her time - turner in a new and creative way. In this kind of fanfiction, she might have to outwit the Ministry of Magic and the Death Eaters who are after Sirius. She could change the course of the story by preventing Sirius from going to Azkaban in the first place.
The theme of second chances is also prevalent. In time travel stories, both Harry and Sirius may get opportunities they missed in the original timeline. For example, Sirius could save his friends who died earlier. And also, the exploration of the past and how it shapes the future is a key theme. They go back and learn things that change their perspective on the present and future of the wizarding world.
Another idea might be that Harry travels back in time and teams up with a younger Sirius. They could work together to prevent certain dark events from happening in the wizarding world, perhaps by changing the course of events related to Voldemort's rise to power. This would involve a lot of sneaking around and using their combined skills and knowledge.
Obviously, Sirius and Harry are the main ones. But including Remus Lupin can add depth. Since he was part of the Marauders and was close to Sirius, his presence can create some interesting dynamics. He can also offer his wisdom and werewolf - related knowledge to help in their time - traveling adventures.
Another good one is 'Time's Ripple'. Here, Hermione discovers a time - travel device and uses it to go back to Sirius's time. The fic focuses on how their different personalities and knowledge from different times interact and create a unique story line.