All the time. I have a re-occurring nightmare that happens only when I have a fever. It's black void that has unfathomably large cubes. Whenever I'm in there there are voices shouting at me from all directions and I have a spearing sense of guilt and dread, combined with the feeling that you get in your chest when you're falling from a high height. (or going down a rollercoaster)It's awful.
I wrote a bit about it here:http://uboachan.net/yume/res/612.html
I had a hallucination once when I had Influenza. My bed sheets turned into a giant GPS and the voice wouldn't shut up.
Never really experienced anything like it since though.
I don't know why, but sometimes I visually hallucinate stuff that appear in my dreams.
The last particularly memorable dream I had when I was sil was years ago. I seemed to be watching randomly spliced together playthroughs of different JRPGs (one of the was recurring), only the screen would glitch up horribly and then return to normal every few seconds. It had pokemon as well, and there was an evolution screen of a Ditto. That glitched up as well.
Yeah when I was a kid I often got 'Alice in Wonderland syndrome' when I had fevers. I'd feel like my body parts were fucking huge and had hallucinations that I was a giant and my blanket was some kind of cave shiftable cave. Also I'd feel I was lying on a bed of nails and I was constantly trying to shift my body to avoid the nails but it never worked. Since then I haven't experienced that again except for last year which was pretty tame, where I had the sensation my face was protruding outwards like a duck bill or something.
I once had a fever and saw a kitschy looking teddybear swinging on a wooden swing, all in the monochromatic blue and white fibers of my sweater that for whatever reason I was focusing on.