When a wily sheep dog catches a pervert breaking in and molesting its flock, it may decide to teach the offender a lesson by giving them a brutal doggy raping. The way they do this is by setting up a fake sheep with a mouse trap inside its fake anus. Obviously, the mouse trap catches the perv with his pants down leaving them open to a terrible raping. Which they then get. Doggy style.
"Oh no!!!! Shepherd's delight!"
See preversions and prevert.