Human: Why is inter-species reproduction and alien-human hybrids so common in science fiction? Assistant: 
Inter-species reproduction and alien-human hybrids are so common in science fiction because they are a common theme in science fiction. Women being impregnated by aliens is a common theme in SF horror films, including "I Married a Monster from Outer Space", "Village of the Damned", "Xtro", and "Inseminoid". The theme has even been parodied, such as in the soft porn "Wham Bang! Thanks You Mister Spaceman".