Cinematic Discussion: When Does Sci-Fi Become Fantasy?

Note: For this discussion, the definitions below are localized to the medium of the motion picture and the genres of science fiction and fantasy films only. Though there are many examples in television, literature, and even video games, here is not the place for such examples to be entered as evidence.

We can probably all agree on the broad-stroke definitions and differences between Science Fiction and Fantasy. Where fantasy, at its most generalized, contains elements of magic, the supernatural, and a plot centralized and dependent on one, the other, or both, science fiction differentiates itself by utilizing elements that, while extraordinary and often times imaginary, are grounded in the basis of actual, established scientific law or scientifically-postulated theory. In other words, Rod Serling's to be precise, "Fantasy is the impossible made probable; science fiction is the improbable made possible." Using these definitions, it's often very easy to differentiate one film from ...