The stuff that dreams are made of
Dreams are the stuff that leaks off as your brain crunches things during sleep.
That stuff that Task Manager on my computer calls "System Idle Processes," a process that sits there and uses up CPU and disk time when I haven't touched the thing in an hour.
Dreams are the brain's attempt to make something out of this, and usually it makes no sense at all. It's like watching the disk drive light and trying to read Morse code out of it.