Its our creativity.
For us....we tend to view other aliens as having two arms and two legs. Just look as mass effect, the only exceptions to this rule are the Hanar the mechanic guys in the citadel, and the big guys who walk on their arms and legs.
For psychological purposes, we usually view aliens more comfortably as having similar body structure to us
If an alien was peaceful, yet had 7 legs, one arm, 30 eyes and 200 teeth, would you still NOT be creeped out by it just a little?
Sometimes they seem to make sense though,
Like the Ridley Scott Alien, it gets Genetics from the host it impregnates, we gave it 4 limbs essentially.
For us....we tend to view other aliens as having two arms and two legs. Just look as mass effect, the only exceptions to this rule are the Hanar the mechanic guys in the citadel, and the big guys who walk on their arms and legs.
For psychological purposes, we usually view aliens more comfortably as having similar body structure to us
If an alien was peaceful, yet had 7 legs, one arm, 30 eyes and 200 teeth, would you still NOT be creeped out by it just a little?
Sometimes they seem to make sense though,
Like the Ridley Scott Alien, it gets Genetics from the host it impregnates, we gave it 4 limbs essentially.