Many years back when I still lived with my mom...my mom bought a Christmas Poinsetta and put it on the back porch. My dog Bear (Mastiff Rotty mix) saw the flower and knew it didn't belong there. He must have barked at that damn thing for 15 minutes.
Of course another time he got a 5 gallon bucket stuck on his head, and wound up running full speed into the power pole. It knocked the bucket loose...and obviously stunned him. He proceeded to bark at the bucket and the pole...then ran off.
I loved that damn dog....