Never mind. Apparently he's been scared every night at bedtime for some unknown reason, and we had a big talk about how he is safe here, his bed is safe, there are adults to keep him safe, and a big dog (who is really all mush and no bite whatsoever, but she is bigger than he is), and that I would never ever ever put him to bed in a place that is not safe.
And, he went to bed. Ugh. Why are kids so complicated???
Mystery indeed. He even sleeps with 2 teddy bears every night (one apparently isn't enough to cuddle with....). He was in a great mood when he woke up this morning too. I dunno. Kids are strange.