I knew already, I’ve seen them in Doctor who last year 
When mannequins attack: “David Pescovitz:
A woman is suing JC Penney Co. after a mannequin’s arm snapped off and knocked her in the head, cutting her scalp, cracking a tooth, and causing other injuries. The incident occurred when a salesperson at the Westiminster Mall store attempted to remove the mannequin’s shirt which the plaintiff wanted to purchase. Apparently, mannequins can be quite dangerous…Link(Thanks, Paul Saffo!)
“
(Via Boing Boing.)