Another similar thing happened to me a couple months ago while putting my 4-year-old daughter to bed. She usually insists on a new, made-up story rather than one I can read to her, or rather than one she already knows like Goldilocks & the 3 bears. Anyway, I was lying on the floor next to her bed, completely exhausted and actually falling asleep mid-sentence. But instead of becoming quiet, I continued the sentence in this bizarre sleeping state of mind, and it quickly became totally absurd. The realization that what I've just said is total nonsense jerked me back to wakefulness. I apologized and couldn't remember what I was going to say, so I started a new sentence, and the same thing happened again. It started out relevant to the story but ended insanely. I think I tried at least one or two more times, before I told her I just had to go to bed because I wasn't making any sense, and she agreed.

If I don't have any music or other white noise going when I'm trying to get to sleep, I'll hear familiar voices -- especially any that I've been exposed to that day -- spouting Markov chain stream-of-consciousness babble. It starts early enough in the process of falling asleep that I'm otherwise completely lucid, though.

It was the same with me. I often had trouble getting to sleep, so when I started hearing people in the room say random phrases, I would think, "Good, I'm finally about to go to sleep. A few more and I'll be out."

Sweet Baby Cheeses - that would wake me the fuck up quick-smart.

No! So no!

Yeah, it did until I got used to it. It still rouses me if the voice is a contextually plausible one, such as hearing my sister’s voice if she is visiting, but a stranger or a random work colleague just slides by, like a neighbor’s dog barking.

I get vivid auditory hallucinations, most frequently napping, but sometimes falling asleep at night. It's usually a nasal female voice saying nonsense. My favorite one was just the word "diarrhea"which made me laugh myself awake

Yup. I know it well. For years in my late 20 and early 30s, especially when stressed out, as I'd be getting close to sleep I'd hear someone in the room with me say random phrases very clearly, like, "before the ground could return," or, "probably blue, even if I could." Sometimes they would be in the voice of a friend of family member, other times, a stranger. It's rare, now-a-days, though.

When I was living in the woods sleeping in my truck I would occasionally be woken up in the middle of the night by a vivid hallucination of the sound of my truck topper's rear window slamming shut. As if someone was looking in at me sleeping. Now that grandma is gone and I'm taking care of my grandfather full time, I'm often awoken by the imagined sound of my grandmother calling my name like the time I had to call 911 for her a couple of years ago. It seems like my brain likes running me through emergency drills from time to time.

Yikes! I've had the occasional door slam sound.

I have been woken up by people really peering in the car window at me, in the middle of the night. When you're sleeping in a situation like that, you stay very sensitive. They ran away when I looked at them.

Salvador Dali wrote about going to bed while holding a key over a plate on the floor. The moment he feel asleep, he dropped the key, and the noise would wake him up and he would use whatever was in his mind at that moment as inspiration.

I've heard that Thomas Edison used to do something similar, for inspiration.

His paintings were rubbish though.

Reminds me of a story by robert silverberg titled, "The Desert of Stolen Dreams.