Doctor Who and Time Warp Trio are in the same universe
- It could be possible plus I want a crossover not for real but fanmade.
This genuinely seems possible with the book being the same color as the tardis and Mad Jack/Uncle Joe could be a future version of the Doctor...
Samantha and Freddi are both descended from both Sam and Fred.
- In one of the generations between the boys and the girls, a descendant of Sam and a descendant of Fred had kids together. By the time the girls are growing up, there's some kind of estrangement that prevented them from being told of their relation but it had dissipated enough for Samantha and Freddi to be allowed to become friends.
- Or they could be sisters whose parents divorced when they were too young to remember and due to the events of the divorce, haven't been told that one of their respective best friends is actually their sister.