7. Leela
You could have knocked me over with a feather when Leela suddenly decided that she'd rather stay on stuffy old Gallifrey than go gallivanting across the galaxy with the Doctor. But then I realized, this is the perfect opportunity for a crazy fish out of water, Perfect Strangers storyline. Just imagine the intuitive yet primitive Leela adjusting to life on the planet that made literally the coolest concept into something dull as dishwater. It practically writes itself. But seriously, I would be interested to see how she adapts to her new environment. She's far more clever than people give her credit for, but will the Time Lords recognize that? I'd love to see if Gallifrey changes her, or if it's the other way around. Then again, people do tend to forget how logical and rational she tended to be...maybe she'd fit right in! Either way, it was definitely a sudden change for the character, and I'd be perfectly happy to watch the rest of her story unfold on screen.