The Fear-Dar is a device invented by Dr. Flurry. Its main purpose is to scan everyone's fears and uses it to freeze the victim. It was placed in the Bumblyburg Science Museum after Flurry's first arrest, but he sent his penguin minions to steal it back so that he can get revenge on the League of Incredible Vegetables.
According to Mike Nawrocki, it is based on an old-fashioned police speed gun.