10 Tragically Romantic Doctor Who Episodes

The first outing for Bill Potts and the Twelfth Doctor sees Bill being chased by a type of alien engine oil, when it takes over the body of fellow student Heather.

Unlike the other entries on this list, this episode features a thwarted crush, rather than an actual coupling. While it is apparent that Bill has the hots for Heather, the two girls have very little chance to really connect before the poor girl is possessed by an alien. Nonetheless, it’s the beginnings of this connection that end up driving the alien force. It now follows Bill everywhere, throughout time and space, determined to keep a promise made by Heather - to not go without her. It is only by telling her to go that Bill frees herself from it. The moment is still tragic though, not only for the potential love Bill loses, but because she is actually tempted to go see the universe with Heather, even doubting her choice for a second, in the Doctor’s study.

Luckily, everything ends pretty happily, as the Doctor offers to take her travelling instead, hinting that they will find Heather again one day.