My mom always says the television watches my dad, not the other way around.
My sister and I spent the night at my parents' house this past Friday. Guests usually sleep in the living room. My dad fell asleep on the couch and we had to wake him up so we could go to bed when the movie was over. It didn't matter that we were all howling through "Blades of Glory" and plain ole chit-chatting. I think the noise lulls him to sleep. He was awake for the beginning of the movie, but he gradually fell asleep.
He's been doing this for quite some time. I was still in high school and he'd come home around 11PM from his second job. I'd be doing homework (procrastinating) and we'd watch some TV together - Twilight Zone, news, Benny Hill, whatever, and talk about what was on or I would listen to him talk about stories he had related to what was on - and he'd eventually fall asleep. He'd sense things were done when the program was finished or when I'd start wrapping things up with my papers and he'd wake up.
On Friday however, a little nudging of his arm wasn't enough going to be enough. When we realized this was going to take a little more effort than normal, I blurted out, "Daddy, wake up now so you can go to sleep." We were laughing so hard, I think that really got his attention. So he said his goodnights and made his way up to the bedroom.