A Creature Catcher is a human who hunts down and captures supernatural creatures like werewolfs and ghosts for a living. They often use advanced gadgets and traps to do so.
The only known creature catcher in the series is Mr. Bradley, who decides to become one after he saw Casper with Jimmy and scared him off. However, it is strongly suggested there are more creature catchers in other towns, since in the episode "Revenge of the Creature Catcher", after escaping from Scare School, Mr. Bradley was seen calling a company named "Creature Catcher Supply" to order new tools for his job.