It seems worth mentioning that Ollie is, and always has been, obsessed with balls. In fact, his first word was ball (at 7 months old). He is also very fond of balloons and bubbles. So, maybe it's just an obsession with round things. I don't know.
But today he enjoyed sitting in his laundry basket (which we call his "Pod", filled with blankets and pillows) and watching Olympic Beach Volleyball with me. He just kept calling out, "baw up, baw dow". He just loved it.
Here are some pictures of him from a week ago playing with a ball in the yard. Needless to say, we always carry a ball with us.