10 Doctor Who Villains You're Surprised Only Appeared Once
5. Rutans
The Sontarans' mortal enemies may look like balls of snot but they're deadly shapeshifters with plenty of unrealised potential. While they've been name checked in the new series, they've never actually appeared in an episode. However, they have appeared in multiple comic strips, novels, fan films and even video games.
It's perhaps the Rutans' jellyfish-like appearance that has barred them from returning to the series after 'The Horror of Fang Rock'. How to effectively realise their appearance without being totally embarrassing probably makes Doctor Who's practical and visual effects teams wake up in a cold sweat. However, the Rutans are shapeshifters. 'The Horror of Fang Rock' is essentially John Carpenter's 'The Thing' in a lighthouse.
No one's sure who's who as this deadly alien works their murderous way through the inhabitants of the lighthouse as they assessed the strategic importance of planet Earth. While 'The Zygon Invasion/Inversion' has already done the shapeshifting political thriller, there's surely plenty of scope for another shapeshifter story in modern Doctor Who. Or perhaps, given 'Flux's epic space battles, the time is right to finally see what a Sontaran and Rutan war actually looks like.