"'—All You Zombies—'" is a science fiction short story by Robert A. Heinlein, written in a single day, July 11, 1958, and first published in the March 1959 issue of Fantasy and Science Fiction magazine, after having been rejected by Playboy.
The story develops the themes begun in the author's previous story "By His Bootstraps", published some 18 years previous, and involves a number of paradoxes caused by time travel. Since its publication, "'—All You Zombies—'" has become one of the most famous science fiction stories about time travel. In 1980 it was nominated for the Balrog Award for short fiction.
Cajoled by the Bartender, the Unmarried Mother explains why he understands the female viewpoint so well: he was born a girl, in 1945, and raised in an orphanage. While a fairly ugly teenager in 1963, he (that is, she) was seduced, impregnated, and abandoned by an older man. During the delivery of her child, doctors discovered she had an intersex condition: internally, she had both male and female sex organs. Complications during delivery forced them to give her a sex change. The baby was later kidnapped and not seen again. The now-former girl had to adjust to being a man and surviving as such, despite being unprepared for any job. As a girl he/she had preferred etiquette lessons, hoping to join an organization dedicated to providing "comfort and companionship" to astronauts, known at various times by the elaborate acronyms "W.E.N.C.H.E.S" (Women's Emergency National Corps, Hospitality & Entertainment Section), "A.N.G.E.L.S." (Auxiliary Nursing Group, Extraterrestrial Legions), and the Women's Hospitality Order Refortifying & Encouraging Spacemen (the only name without its acronym spelled out in the story). Handicapped by the physical aftereffects of childbirth, he used his secretarial skills to type manuscripts, and eventually began writing.
Professing sympathy, the Bartender offers to top his story. He guides him into a back room, and casts a net over the two of them. This is part of a time machine. The young man is set loose in 1963 where he dates, falls for, seduces, impregnates, and leaves a young girl; at the same time the Bartender goes forward nine months, kidnaps a baby and takes it to an orphanage in 1945. He then returns to 1963, and picks up the Unmarried Mother, who is just beginning to realize what has happened. As the Bartender tells him, "Now you know who he is—and after you think it over you'll know who you are . . . and if you think hard enough, you'll figure out who the baby is . . . and who I am."
The Bartender then drops the Unmarried Mother—his younger self—at an outpost of the Temporal Bureau, a time-traveling secret police force that changes events in history to protect the human race. He has just recruited himself.
Finally the Bartender returns to 1970, arriving a short time after he left the bar. He yells at a customer playing "I'm My Own Grandpa" on the jukebox. Closing the bar he time-travels again to his home base. As he beds down for a much-deserved rest, he contemplates the scar left over from the Caesarean section performed when he gave birth to his daughter, father, mother and entire history. He thinks "I know where I came from—but where did all you zombies come from?", possibly referring to the rest of the humanity, those whose existence did not come from his own closed loop of creation.