I know that similar versions of this question have been asked, even by me.
The line in question of the enlarge person spell says:
Target one humanoid creature
I ask because earth elementals are described as:
This hulking, roughly humanoid creature of dirt and stone explodes up from the earth, faceless save for two glowing gemstone eyes.
Thus, an earth elemental is humanoid in form but not type. Does the spell work on things with head(s), arm(s), leg(s), and a torso?