My thrashing startled him and woke him up completely. He asked what was wrong, but I said "nothing," rolled over and went back to sleep. I was aware that it had been a dream, but I was still completely convinced that there was a spider from outer space still on his pillow. But that's just crazy, so I had to leave the alien spider there and go to sleep.
It turns out that I could've finished brushing the dream spider away because HA was so awake that he went to the couch to watch a DVD and fall asleep (which he does fairly regularly because of his insomnia).
The amazing thing? He's not pissed that I started beating his pillow in the middle of the night. He says that I didn't do it on purpose and he's probably just relieved that I wasn't having a seizure.
Though maybe I should be mad at him for leaving me in the bedroom with a dream spider that was trying to get me. Because that's just rude.