I don't understand how the brain selects what to dream about.

Last night I had a dream that I'd discovered I had long hair growing from my feet - like several inches of head hair all over - and I didn't want to shave it because the stubble would be painful.

I'm guessing that came at least in part from getting stabbed in the foot yesterday by what was either a splinter or a short piece of hair, and then briefly examining the sole of my foot in case there were more - but why dream about that rather than any number of other trivial/unusual events... unless I did, and that's just one which happened to occur before waking... *shrug*

I've definitely invented locations, but mostly they tend to be corruptions and/or combinations of real places - it's weird when it's somewhere I know well and can imagine with reasonable accuracy in my awake brain, but my sleeping brain renders those memories differently.