Tales from the Darkside - Season 3 Episode 13 The Milkman Cometh

A man, Garry, hears from his neighbor a bizarre tale of how the unseen neighborhood milkman grants wishes to anyone who leaves their request in the empty bottles to be picked up. Garry tries it for himself and soon finds his every wish granted. His final wish is for a daughter, and his curiosity is too great and he tries to confront the milkman. Garry gets a glimpse of a deformed mutant creature before it disapepars and then realizes exactly how the ""milkman"" will fulfill his wish - by impregnating his wife.