One more parallel-world post

Since I brought the subject up, let me touch briefly on one of the hoariest parallel-world/time-travel cliches: The exact double of the protagonist’s lover.
In the Bing Crosby version of A Connecticut Yankee at King Arthur’s Court, Crosby falls madly for a young noblewoman whom he leaves behind when he’s yanked back to the present. Surprise!—he runs into her distant descendant and exact lookalike, so he hasn’t lost her after all!
Likewise, in Quest for Love, the protagonist is yanked into a parallel world where his counterpart is an obnoxious shit and has to win back said counterpart’s lovely young wife, Joan Collins. When he returns to our world after her death from a heart weakness, he runs a desperate race to find her counterpart before she dies from the same weakness (and succeeds).
In both cases, the assumption is that it “is” the same person, even though it obviously isn’t: A 20th century woman is not going to be the same as her Arthurian-era ancestor, and the two Collins have lived very different lives (they’re more like identical twins separated in childhood).
Not that I can’t buy it if I like the movie, but it’s still slightly ridiculous.