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Mrs Poggit was an elderly human living in Upper Leadworth. Mrs Poggit lived in the old people's home with the rest of the pensioners of Upper Leadworth.
In the fake world created by the Dream Lord, Mrs Poggit's body was taken over by an Eknodine, a member of an alien race who fled their world and lived in the bodies of old people, keeping them alive for many years. When the Eleventh Doctor, Amy Pond and Rory Williams woke up in the dream world, she asked the Doctor if he could try on the jumper she was knitting for her nephew. As he did, he examined her, saying that she was really old, older than any normal human, before he fell asleep again.
Soon, they noticed Mrs Poggit walking to the children's playground and wondered what she wanted. When they woke up again, they found all the children were dead, and that they were killed by Mrs Poggit. The aliens who had taken over the pensioners, had an "eye" in their mouths, which could release a gas to disintegrate their enemies. They did this to people as they wanted revenge for what had happened to them. When the Doctor confronted them, the postman arrived but Mrs Poggit killed him.
They escaped, but Rory and a pregnant Amy were trapped in their house's nursery. After the Doctor climbed through one of the windows, Mrs Poggit climbed to another and killed Rory. The Doctor whacked her with a lamp, causing her to fall off the roof. Later, she bore an axe just before the Doctor and Amy crashed the camper van, ending the dream.
Biography from the TARDIS Data Core article, licensed under CC-BY-SA