I went to clean my Burmese python's enclosure last night several hours after lights out at 10pm. I usually do maintenance during the day but he had pooped and I wanted to take care of it. I thought I startled him but he was actually still asleep. He was hissing and having dream twitchies (like dogs when they growl and "run" while sleeping). Then he twitched awake and scared himself, looked at me, and lied back down. He stretched and curled back up. Poor guy lol ...it's hard to tell when he's sleeping because he doesn't have eyelids. He was deeply asleep too. I think he actually may have been in REM. I tried to do some research to see if reptiles enter REM and the internet says they don't as far as I can tell. I have my doubts about this.