Socks Monsters exist on Sock Planet. Sock planet is where all the socks go when the worm-hole in the dryer opens up due to build up of static electricity. Sock planet is the reason you only get 1 stocking at Christmas.
#5 is the sock worms, created by the Sock Witches (Sockmonster3).
They are a parasite or para-sock. They feast upon other non-sock creatures. They are about the size of heartworms, and you do not want them inside, of you, as they eat you from the inside-out. They multiply like fruit flies.