Dream or fiction?
Let improv be closer to dreams than fiction.
This perspective encourages us to embrace absurd and unpredictable elements in our scenes.
Dreams are more interesting than fiction, because fiction stays rooted in reality, even when it gets fantastical. Not all your scenes need to be strange or absurd (just as not all dreams are), but going dream-like from time to time can make things way more interesting.
Keep in mind that even in a dreamworld, certain rules still apply; it just means that impossible things are now regarded as normal (think Márquez or Murakami, for instance). Fiction has its limitations, but dreams know no boundaries. Let's not box in our improv with unnecessary restrictions.