Two things, both related to me being sick.
The worst was fever hallucinations, lying in bed unable to sleep because at all times I could see dark figures looming over my bed or shadows moving around in the room, or something worse like the bed being full of disgusting bugs or ants crawling all over my body...I hope I never experience that again, that was some crazy [censored].
There was also a time when I was a lot younger when I was kind of sick, and then my legs started hurting like crap, eventually it stopped hurting but I couldn't walk...like at all, my legs just wouldn't move. I never figured out what it was, but my dad's theory (he's a doctor) is that it was just extreme growing pains, which makes sense as it's never happened to me before and I'm perfectly healthy right now.
Another wierd thing that used to happen to me is I think I used to randomly faint, but I could never be sure. I just sat there feeling like I'd been out for a few minutes.
That's happened to me two times when I had a very high fever. the only time I can remember was last time I was sick, I got out of bed rather quickly because I thought I had to throw up, got to the bathroom and then nothing happened, so I had some water, walked out and...that's all I remember, I woke up when my mom yelled my name as she found me unconscious on the other side of the room, I have no idea what happened before I blacked out, suddenly I was just on the other side of the room. Again, the main theory is that my bloodsugar has gotten to an extreme low in those cases, and I've put to much stress on my body and just passed out, whenever I feel like that I usually lie down with my legs high and wait, it's only happened when I've been sick, so I'm not really worried about it. The big advantage of having your father be a doctor and your mom a nurse is that I can usually get whatever I need if I'm sick.
When it happens my face is drained of all colour, I start breathing heavily and feeling like I'm about to throw up, then I'm just gone.
Second time this year that I hallucinated when I got out of bed quickly. I don't know the reason why.
A common technique to induce lucid dreaming is inducing sleep paralysis first to make yourself aware that you're dreaming, it's possible your brain just kept on dreaming for a bit after you got up very quickly. I'm by no means an expert on these things though, so take this with a grain of salt.