Three humans have currently appeared in the One True Comic: Megan, Cueball, and LaPetite. They have been depicted as stick figures. It is unknown if they are actually stick figure or if that is just the way Randall has depicted them. It is also unknown whether they are wearing any clothes besides LaPetite's hat.
For information on humans that have not appeared but have been mentioned by Cueball or Meagan or are theorized to exist, see The Others.