"cut your legs off"

Courtney would not sit still at dinner tonight. She is probably the worst of the three these days mostly because she stands up on her chair and eats. Jon and I were getting mad at her. We told her she wasn't getting a Christmas cookie if she didn't sit still. That didn't work she was still standing on her chair. Then Jon said if she didn't sit down he was going to" cut her legs off at the knees!" She sat right down. Then about 60 seconds later she stood up again and looked at Jon and said "please don't cut my legs off!" and she sat back down!