Oliver would play fetch 24/7 if someone would throw his little tennis ball for him. But we won't. So one day we heard "thump, thump, thump...patter, patter, patter...thump, thump, thump...patter, patter, patter..." You get the idea, we just kept hearing it. Come to find out it was Oliver, on the deck, dropping his tennis ball at the top of the stairs, letting it bounce down the steps, then running down to fetch it. Back up, repeat.