From a scientific side, I remember from 8th grade being told that dreams actually last no more than a few seconds and your brain’s imagination fills in the gaps and expands it once you wake up.
Vaskania - I remember dozing off on the sofa one day, and getting to that half-asleep/half-awake state. I was disturbed by the door opening, and I vividly recall three distinct images - the front door of a house, a briefcase, and a refrigerator. But as I woke up they merged into a short sequence - I opened the front door of my house (which became a refrigerator door as I opened it), and put my briefcase into the refrigerator. Weird, eh?
Jaderail - Lucid dreams? I’ve had one or two semi-lucid ones, where I become aware that I’m dreaming and partially take control. I say partially, because it never goes quite how I want. Like once, deciding to make myself fly and managing to float up into the air, but being totally unable to move sideways, and having this strange feeling that my subconcious was laughing at me and saying “so you think you’re stronger than me, eh!”
I also remember reading about ‘hypnagogic hallucinations’, the scientific term for those visions/dreams you get as you’re waking, with your eyes open, but your body paralysed. I used to get them quite often, and I’d be too scared to go back to sleep. After discovering a rational explanation for them, I had no problem getting back to sleep. But they were still terrifying while they were happening.
(Personally I much prefer LOL dreams to scary ones)