Simon has gotten up a few nights in a row a little more upset then he has been able to deal with. While many suggest he's enduring night terrors, I doubt that's it. The clinical definition tends to peg kids at 4 to 12-years-old, and occurring in 1-6% of that group. It also says the kid will typically appear awake but inconsolable, and Simon is fine as soon as you pick him up.
That said, I certainly believe he's had bad dreams, or that his imagination is getting the best of him. I remember having my share of darkness fears at that age (pegging the age because it was before my brother was born). Mine was a repetitive dream, featuring a scary music box, and when the lights came on, the creepy lamp with balloons (and maybe a clown) in some ways made it worse.
Simon chills out when you pick him up and turn the lights on. The other night, I actually brought him into the spare room and crawled into bed with him, and when I asked him if he was ready for bed, he took it upon himself to go back and crawl into bed himself. Tonight he appeared almost physically sick, shaking and sweaty. He sat with Diana for a little while and went back to sleep.
To this point, I've been pleasantly surprised at how relatively independent he has been about bed. After the first couple of weeks sleeping in a bassinet in our room, he has slept on his own in his room. A few weeks ago we converted his crib to a toddler bed, and once he's ready, he climbs up in on his own. Lately he doesn't even want you to tuck him in, he'll just sit up until you leave.
I'm sure this will pass soon enough.