A less commonly celebrated milestone?

Apparently, in Henry's case and in the case of a few other babies, according to the Internet, the crawling milestone goes hand in hand with the sitting up by himself in the crib milestone. This particular milestone seems to be less appreciated by parents. Why? Because its kinda creepy. A few mothers had asked us if we had encountered the shrouded baby figure sitting up alone in the crib in the middle of the night. Not crying, not complaining, just sitting. In the dark. Alone. With a blanket over its head. Ok, that scenario didn't exactly happen to us (although, it reminds me of that movie with Nicole Kidman. I think it is called "The Others."). Instead of sitting up in the middle of the night, Henry sits up in the morning, sits up after naps, sits up when we are trying to put him to bed...

The other morning Mike entered Henry's room to find Henry upright and smiling - Mike was startled. The same thing happened to me on Saturday when I heard Henry stirring after his nap, there he was sitting up and hanging out (see above picture). Last night, Henry popped up as soon as we set him in the crib for bedtime. He remained upright so we left him that way. We could hear him in his room babbling and moving around, but he was quiet and seemed content so we just left him alone. About 45 minutes later, I checked on him and found him sitting up in his crib but slouched forward - he was asleep in the sitting up position. I arranged him in a comfortable position and he slept through the night without a peep.