They also have sensors that can sense loud sounds , they can sense being upside down ( they say things like `` Shiver me timbers '' and `` Walk the plank '' , in the style of a pirate ship captain , when you leave them upside-down for a long period of time ) , and they laugh when you `` tickle '' them ( their antennae - or `` tennies '' , as they like to call them ) . They also have sensors that can sense loud sounds , can sense being upside down ( they say things like `` Shiver me timbers '' and `` Walk the plank '' when you leave them upside-down for an extended period of time ) , and they laugh when you `` tickle '' them ( their antennae â `` or `` tennies '' , as they like to call them ) .