S04E20: Small Potatoes
This is a beauty written by Vince Gilligan, where the story starts with Mulder and Scully investigating a town where babies have been born with tails, but the case turns on its head when they discover that the babies all have the same father... which would appear impossible.
Enter Eddie Van Bundht, who is a much more intriguing character than it initially appears when he is confirmed as the father of all five children. A bit corny in places, but this is an enjoyable X File all the same. 4.5/5