You feel something gooey on your skin and realise you're taking a bath full of ketchup. You find yourself in the middle of the desert riding a fish, or you're at the fishmonger's in a state of undress. All these scenes may seem fantastical, but they're a figment of our imagination. 

When we sleep, we call them dreams. All these scenes are the accumulation of things we have seen during the day or in the days preceding the dream. They remain hidden in our subconscious until our brain decides to associate them and thus create these completely incongruous moments of life.