How does your brain produce an image of something you've never seen?

Imagine, for a second,a duck teaching a French class,a ping-pong match in orbit around a black hole,a dolphin balancing a pineapple.
You probably haven't actually seen any of these things,but you could imagine them instantly.How does your brain produce an image of something you've never seen?That may not seem hard,
but that's only because we're so used to doing it.It turns out that this is actually a complex problem that requires sophisticated coordination inside your brain.That's because to create these new, weird images,your brain takes familiar pieces and assembles them in new ways,