Designing Plausible Aliens (WIP)

interbreedable hominid = no
eldritch horror = no

chimeras = yes

uplifted animals = yes
genetic engineering = yes


universal
+ bilateral symmetry
+ internal skeleton

likely
. head with brain, mouth, most sensory organs
. 2+ eyes capable of facing forward
. limbs attached to one or more additional segments
. 2+ arms, 2+ legs
. upright posture

options
. senses: eyes (possible ), ears or antennas, nose or antennas, mouth w/tongue
. mouth: teeth, beak, maybe mandibles
. skin: slimy, smooth/thin, leathery, hair, downy feathers, scales
. locomotion: bipedal, centauroid, part-arboral, amphibious
. head/face: eyestalks, antennas, horns, tusks, crests, etc
. body: armor plates or shell, extra limbs and/or wings, tail

weird:
* hearing might be distributed

never
. interbreedable with creatures evolved on other worlds
. exoskeleton
. tentacle walkers
. fully aquatic

options

TnA
. Tits = possible (some non-mammals also feed secretions to their young)
. Butt = likely if bipedal and tailless