My mom's godchildren had Furbies, and they would put them in a drawer and close it when the Furbies were "tired" (they needed darkness to "fall asleep"). Then the little things would become terrified and start making their fear noises, like they were being punished for something.
They brought the Furbies with them on a trip with my family once. It was rather creepy when we were trying to sleep and the Furbies wouldn't shut up; instead, they continued to mumble cryptically from the depths of a drawer, even when we finally took the batteries out. Eerie little buggers.
Here's one way to solve the problem of a malfunctioning Furby:
http://www.phobe.com/furby/