AH.com Series episode by Dave Howery. The crew need a vacation, but are barred from most of the big vacation timelines for past incidents. Doctor What finds a more obscure but still welcoming one, but his brochure is 20 years out of date. When they arrive, the crew find that only one of the resorts on the planet is still working, the rest of the planet desolate. Two security teams beam down and are immediately captured by anthropomorphised animals working for 'Mr Tiddles', a cat-man who has converted all the humans he could find (after a great plague that killed most people) into other anthropomorphs who are brainwashed into serving him.
Tiddles manages to convert most of the captured security teams, but the rest of the crew are busy making contact with the human resistance led by the local The Bald Imposter. They learn from a captured anthropomorph (who later turns out to be Jessica Alba) that their 'god' lives on the top floor of the resort. Inevitably, it turns out to be Highlander, whose project was wrested out of his control by Tiddles and has been trapped there ever since. Highlander is freed and he and Tiddles accidentally kill each other. The AH.commers use Tiddles' machine to revert all the furries to humans.
We learn in the episode that Keira Knightley, being an artificially created life form, only has a very simple genome, and that Dave is worried that if she is ever exposed to any kind of genetic manipulation like Tiddles' machine, she'll die.