I heard the dog story as an incident in a tourist trap on the coast of Maine. A local enters the store and asks who owns the great Dane (Saint Bernard/Newfoundland/etc. take your pick as long as it's big) tied up out side. Mr. Tourist steps forward and says it is his dog.
"Good dog?"
"It's the best!"
"well bred?"
"It has pure bred papers going back 10 generations. Why all these questions?"
"Well, it appears my dog has killed your dog."
"What! What kind of dog do you have?"
"Chihuahua."
"No! How on Earth could a Chihuahua kill a Great Dane?"
"He got stuck about halfway down his throat."