Simple categories matching alien:

• genus,
• grass,
• hero,
• person,
• beast,
• animal,
• species,
• substance,
• shrub,
• tree,
• plant,
• pest,
• being,
• race,
• relative,
• entity,
• material,

Members with property alien:

• Superman,
• Kal_El,
• bradford_pear,
• qin,
• japanese,
• minor_child,
• beard_grass,
• hero,
• gray,
• strongman,
• pesticide,
• aphid,
• banana,
• crime_fighter,
• drug,
• sand,
• mullein,
• Spider-Man,
• australian_eucalyptus,
• mite_dust,
• Ilya_Kuryakin,
• fish,
• italian_pine,
• teasel,
• fabric_lint,
• kudzu,
• Wolverine,
• sibling,
• tilapia,
• knapweed,
• mongoose,
• lantana,
• west-indian_lobby,
• Napoleon_Solo,
• mesquite,
• dandelion,
• chemical,
• wild_tamarind,
• rhododendron,
• feral_goat,
• jacaranda,
• ink,
• Catwoman,
• fertiliser,
• various_grass,
• cinnamon,
• Matt_"Daredevil"_Murdock,
• small_grey,
• rat,
• gnat,
• cigar_smoke,
• chamois,
• australian,
• pig,
• arsenic,
• poplar,
• plant,
• smoke,
• deer,
• acacia,
• melilotus,
• ginger,
• pine,
• feed,
• cactus_species,
• inorganic_mineral,
• evil_god,
• bramble,
• australian_myrtle,
• spouse,
• eucalypt,
• dog,
• casuarina,
• goat,
• cane_toad,
• sheep,
• ammonia,
• food_dregs,
• australian_wattle,
• cocklebur,
• brood,
• cat,
• formosan_termite,
• syzygium_jambos,
• parent,
• honeysuckle,
• daphne_laurel,
• silky_oak,
• canadian_pondweed,
• gorse,
• buckthorn,
• wife,
• black_wattle,
• grevillea,
• oil,
• pinus,
• ship_rat,
• dirt,
• carp,
• leafy_spurge,
• lantana_lantana,
• cereal_grain,
• cheatgrass,
• herbicide,
• grey,
• ant,
• agricultural_chemical,
• fungi,
• hydraulic_fluid,
• big_bluestem,
• cork,
• black_rat,
• terrapin,
• honeysuckle_lonicera,
• mediterranean_palm,
• acacia_cyclops,
• camphor_laurel,
• trout,
• smooth_brome,
• syringa,
• united_state,
• bass,
• himalayan_balsam,
• wattle,
• eucalyptus,
• type-a_grey,
• reptilian,
• cotton,
• rabbit,
• child,
• prolific_mullein,
• dust,
• rodent,
• gum-tree_eucalyptus,
• autumn_olive,
• ancients,
• hilo_grass,
• Deadpool,
• heather,
• gum,
• Green_Lantern,