I was on a charity ride in east Texas and had two "unpaid participants" in about 10 miles. The first was a little wiener dog that was hiding in the tall weeds next to a corner. He jumped out barking and and I just about lost it. He had the ambush plan down pat. The second dog was just out for a good time. He was a larger pit type dog, in good shape and about as tall as my front tire. I know this because he spent about 3/4 of a mile playing like he was going to bit the tire. He just loped along and every 4 or 5 pedal strokes, he would make a little lunge like he was going to grab for it. I could not go fast enough to leave him so I finally scuffed him off by getting too close to a plow being moved by a farmer down the road.
My favorite non-bike story was a friend had a bull mastiff that liked to ride in the back seat of her convertible. One day she pulled up w/ the dog and said it was the best day, Samson slimmed a motorcycle cop.