When there is a romance (in a game, movie, book, or other media) that involves members of two separate species, generally sentient, otherwise it is bestiality. This can refer to either extraterrestrial beings, or sentient creatures from our own planet (such as those reptilian human things from Dr. Who)
Common interspecies romance couples: Garrus/Shepard, Troi/Riker, Dr.Who/Amy, Arbiter/non-elites, Spock/Kirk is a homosexual example, Spock/Uhura
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