alert
alien
attention
ban
believe
cartoon
caution
character
circle
communication
danger
design
element
extraterrestrial
fiction
flying
forbid
forbidden
graphic
hazard
icon
illustration
information
invasion
isolated
martian
monster
mystery
no
no entry
object
prohibited
prohibition
red
safety
science
ship
sign
space
spaceship
stop
symbol
transport
ufo
unidentified
warning
white
zone