Extraterrestrial beings Human-alien encounters 90 Life on other planets 35 Extraterrestres 30 Interplanetary voyages 25 Time travel 19 Imaginary wars and battles 18 Máis ... Space warfare 14 Rencontres avec les extraterrestres 12 Science fiction, American 12 Vie extraterrestre 12 Exploration 11 Families 11 Interracial marriage 11 Parents of exceptional children 11 Science fiction 10 Seres extraterrestres 10 Ethnicity 9 Friendship 9 Parents of racially mixed children 9 Military deserters 8 Interstellar travel 7 Superheroes 7 Exobiology 6 Good and evil 6 Monsters 6 Robots 6 Science fiction films 6 Space and time 6 Teenagers 6 menos ...