The kids in every Vacation movie
Clark and Ellen Griswold (Chevy Chase, Beverly D’Angelo) were so focused on spicing up and keeping their marriage intact, they never noticed Audrey and Rusty were abducted and replaced by body snatchers every few years; across 4 movies, Griswold spawn were played by 4 different pairs of actors. Maybe more attention should’ve been paid: only the first Vacation is Certified Fresh, though Christmas Vacation manages to eke a Fresh score at 64%.