Dreams are basically simulations of our lives that we run, sometimes with different physical constants, resulting in different worldly behaviours. Fever dreams (not necessarily during a fever) are when we are sweeping over a range of constants, so behaviour keeps on changing.
The interesting thing is that dreams are what the mind can do, without the boundaries of reality, such as gravity. This is why electronic devices almost never work in dreams as your mind can’t simulate the logic of their behaviour.