About once every week or two lately, Ari wakes up in the middle of the night to 'play'. I don't have a better explanation. The waking up isn't abnormal, he still wakes up to nurse 3-5 times a night. It's the staying up that's different. He wakes up sometime between 3:30 and 4:30, and I change his diaper, and he plays for a few minutes, and then we spend about an hour trying to get back to sleep. I let him play as long as he's happy, but that wears out quickly and he realizes he really shouldn't be up, but can't get back to sleep. It's getting to be fairly predictable. I'm really not complaining. He's pretty sweet.