When you sneak into someone's home late at night and steal his or her mother away. After apprehending said mother, you cut her open and put candy inside her. She is then deployed at a birthday party for the enjoyment of children.
(I recommend using samurai sword over baseball bat due to its superior cutting capabilities)
Sara: So what can we do for his party?
Tyler: Let's get him a mama pinata.
Sara: Good call. I'll meet you at Crab's.