You could write a story about their adventures in a different time and place. Maybe they encounter a new threat that tests their friendship and skills.
It could be a humorous adventure story where Master and Ten team up to solve a mystery involving lemon-related oddities in the Doctor Who universe.
You could come up with a story where they team up to face a powerful and ancient evil that threatens the entire universe.
You could have a fanfic where they team up to face a common enemy in a new adventure.
You could write a story where the Doctor and the Muppets team up to save a magical world. It would be full of fun and adventure!
You could write a crossover story where the Doctor teams up with the Avengers to save the universe from a combined threat.
You could imagine a scenario where Doctor Who and The Avengers team up to save the universe from a time-traveling threat. Maybe there's a villain manipulating timelines, and both teams need to combine their skills and knowledge to stop them.
There could be all sorts of fanfiction. Maybe they have wild reactions or get inspired to go on their own adventures.
You could write a story where she has adventures in time and space inspired by her love for the show.
It could be a humorous and wacky story where Doctor Who meets baby-talking characters in unexpected situations, leading to lots of funny and chaotic adventures.
One possibility is a tale where a Time Lord gets involved in the Game of Thrones' political intrigues and uses time travel to change the course of events. Or imagine if a White Walker was accidentally transported to the Doctor Who universe and caused chaos.