What movie is it called?

ok theres this movie i can rember what happens in it but i cant rember the name of the movie its about a dog who looks the target dog and he is a friend to a mail man and a bad guy is trying to steal something from the mailman or the dog that i cant rember and the dog bites one of his nuts off and at the vary end both of his nuts are gone and he has the clankers as a subsatot and hes walk down the jail hall way and while he walk it clanks