" What really matters is that in the Star Wars series, as in many works of literature, “I am your father” moments and their accompanying shivers are defining. They involve pivotal transitions and reversals of course, which nonetheless maintain (enough) continuity with the previous story, which now changes and gets more interesting. Vader’s fatherhood also created a significant challenge for Lucas, because it meant that viewers had to reassess past scenes, sometimes in fundamental ways. If the reassessment produced utter incredulity in the audience—not an “OMG” but a “WTF?”—the “I am your father” moment would not work. In fact it would have backfired, ruining the whole series. "

― Cass R. Sunstein , The World According to Star Wars