I find your lack of faith disturbing...
Remember, we're talking about Science Fiction, I'm sure they'll find a way to keep the show going. I bet it'll be something like body swapping or a transformation of appearence.
The Zarbi dissapointed me, they looked like bipedal picnic ants.
(NOTE TO THE CONFUSED: We're pretending it's the 60s and making fake speculation on the old Doctor Who.

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