We mowed part of the lawn earlier, and left the lawnmower sitting in the side yard. A while later, the girls and I let the dogs out, and sat on the deck talking and patting the dogs. Suddenly Impy let loose with his "Alert! intruder!" bark, which sounds like boo-woo-woo-woo!, and took off for the edge of the yard, yapping ferociously. Hero followed him to that side of the yard, growling, and all the fur on his shoulders stood on end as he spotted what Impy was barking at. They both stood there, barking defiance at the scary intruder, and bravely protecting their people and their yard.
Of course, you've probably already guessed that the terrifying intruder was... the lawnmower. We finally had to put it away entirely to get them to calm down.