The mysterious door opener

When we put Andrew down to bed at night, we leave his door open halfway and the outside bathroom light is left on. When we go to bed ourselves, we close his door in order to keep the room sufficiently warm. For the same reason, we keep our door closed too. The last 3 nights, I have woken up to find that both our door and Andrew's door is open. The first time it happened, I got up, closed the doors again and went back to sleep, or at least tried, but I was a little bit alarmed and heard noises (probably in my head), thinking someone was inside. That morning, I woke to discover the doors open again. After two more nights of this, we have come to the realization that Andrew is getting up and opening the doors in the middle of the night! I find it so strange, but also very cute, for several reasons. Andrew never once climbed out of his crib. (we were lucky) Once he got the big boy bed, things changed however. He started getting out quite often, but would come to us (and usually I would hear the footsteps coming down the hall) but there were occasions when he scared me as I woke suddenly to feel something poking me. Most other times, he would stand inside, calling for "Mommy" or Papaaa" and tell us that it was dark, that he wasn't sleepy or that it was time to get up. We put an end to this, simply by telling him before bedtime to stay in bed and as a reward, he would get a new toy (little animal from the bag) for staying in bed. So, it's really quite unusual that he's now just slipping out of bed ever so quietly and opening the doors. I wish that we could leave the doors open for him, but it just gets quite chilly and with Ryan still in our room, we need to make sure the room stays at a comfortable sleeping temperature.