Cantor proved that for any two countable dense subsets of the real line there is a homemorphism from the reals to the reals mapping one countable set to the other. Can the homeomorphism be analytic? This question has been answered periodically (about every twenty years) since Cantor's result was published. However, looking at Cantor's original paper reveals that the very next article in the journal is by a student who extends Cantor's theorem to analytic functions.