My child. What can I say? He loves to laugh. He loves to make people laugh. He loves to make himself laugh. So when I was trying to get him to sing his ABC (which to him apparently means A-B-C-H-Thomas. . .) why would this be any different.
If you watch the video, you'll notice the exact moment where he figures out where the little camera is built in to the computer and the effect that it has on the screen when he moves closer to it. Personally, I think he just likes looking at himself;-)