In a time travel fanfiction, their son could go back to the moment when Jon and Daenerys first met. He could subtly change their initial interactions to make them trust each other more quickly. This could lead to a stronger alliance from the start. He could also travel to the times when they faced their biggest challenges individually and offer solutions. For example, when Daenerys was dealing with the slavers in Slaver's Bay, he could give her ideas on how to end slavery more effectively and gain more loyal followers, which would have put her in a better position when she reached Westeros.
There's 'Time Traveling Dragons' which is an interesting take. They are sent back in time to a period where dragons were more common. Daenerys gets to see how her ancestors interacted with their dragons, and Jon is there to support her. The story has a lot of twists and turns as they try to find a way back to their own time while also changing some things in the past for the better.
One idea could be that they travel back to the time when the Targaryen dynasty was at its peak. Jon could see Daenerys in her element as a Targaryen princess. They might try to change some of the events that led to the downfall of the Targaryens, like preventing the Mad King's actions. But this could have unforeseen consequences for the future they came from.
One interesting storyline could be their journey together after uniting their forces. Maybe they face a new, unexpected threat that tests their relationship and leadership. Another could be a story where they have to navigate the political intrigue of Westeros together while also dealing with their growing feelings for each other.
It would greatly affect Jon. If their son travels back to the time when Jon was still at the Wall, he could reveal to Jon his true identity earlier and help him accept his Targaryen heritage more smoothly. This could change Jon's actions and decisions. For Daenerys, the son could give her more confidence in her claim to the Iron Throne by showing her the future support she could have had.
One interesting plot could be the twins growing up in a post - war world. They might inherit the leadership qualities of their parents, Jon and Daenerys. The story could focus on how they are trained to rule and bring peace to the Seven Kingdoms.
One possible plot could be Hermione using her knowledge to help the Marauders in some way. For example, she might assist them in dealing with a difficult spell or situation that they were struggling with in their original time. Another plot could be her trying to change certain events that she knows will have negative consequences in the future, but then facing the moral dilemma of interfering with time.
One possible plot could be that Android 18 and Goku time travel to the past to prevent the Androids from ever being created. They might face challenges like dealing with the Red Ribbon Army before they start the Android project. Another plot could be that they travel to a future where the Earth is in ruins and they have to find a way to change the events that led to it. They could also time travel to an alternate timeline where Goku was never sent to Earth and see how that changes everything.
One possible plot could be Naruto using the Rinnegan's time - travel ability to prevent the Uchiha massacre. He could change the course of history and save Sasuke from a life of revenge.
In fanfiction, one way it could be possible is through some sort of magical spell or ancient artifact. Maybe there's a long - forgotten Targaryen relic that has the power to manipulate time. When their child discovers this relic, it accidentally sends them on a time - traveling journey.
Another plot could be that they meet under very different circumstances. For example, Jon is sent as an emissary to Daenerys much earlier in the story. At first, Daenerys is skeptical of Jon's claim to the North and his intentions. However, as they spend time together, they discover a shared history of their families and a mutual desire to make Westeros a better place. This discovery leads to a strong bond between them, and they start planning strategies to reshape the political and power landscape of Westeros together.