Yes that is a vent bubble, Lance and his siblings would do this when they were younger and I guess they even had a little song to go with it " the heaters on, the heaters on"... silly Studes. One day when it was colder then normal in our house he decided that it would be fun for Avi. (I really think he was just cold because he is actually in the bubble in this photo)
Avi didn't go in because it was to dark but she did like the fact that it held her shoes up and any other thing she could throw in it.
she is saying cheese... this is very rare now.