Doctor Who: 10 Storylines That Will Never Be Revisited

The Doctor's Daughter introduced audiences to Jenny, an ass-kicking soldier who was created using the Doctor's DNA. The title of the episode was a little clickbait-y since she wasn't the Doctor's offspring in the traditional sense - she was just created in a machine using a few of his cells.

Still, origin aside, the character was a really neat addition to the Whoniverse, a direct relation of the Doctor's... who actually didn't mind using a gun. Not that she was a cold-blooded murderer or anything, but she had a much more combative spirit than the Time Lord, and her fiery personality made for some interesting confrontations between the two characters.

But as the episode progressed, they slowly came to understand each other, so much so that Jenny ended up taking a bullet for her old man, dying in his arms. The Doctor then left, but, surprise! Jenny wasn't actually dead. She sprung back to life on her deathbed, vowed to explore the universe, jetted off in a spaceship, and then the episode ended.

And we never saw her again.

Jenny did appear in a handful of comics and audio dramas, but as far as proper episodic material goes... she's been absent for over a decade. For such a sequel-bait ending, that's just bizarre. Steven Moffat and Russell T Davies have joked that she flew into a moon and died offscreen, which tells you exactly how much the two writers cared about bringing Jenny back for another adventure.