Abstract: An effective, dependable, and humane animal training device employs negative reinforcement to discourage undesired behavior in household pets, especially dogs. An ordinary mousetrap is combined with a flapper which attaches to the spring biased jaw or spring member. This flapper includes a broad face which moves suddenly when the trap is sprung startling but not injuring the animal when triggered by the animal during the inappropriate behavior. The flapper is generally planar and includes molded-in score lines to guide the trimming of the flapper to accommodate different sized dogs.