Real World article
(written from a Production point of view)

A penguin, a type of avian animal in reality, was referenced in the final draft script of the Star Trek: The Original Series episode "Charlie X". In that teleplay, Doctor McCoy jokingly agreed to give Charles Evans some "voodoo and superstition lessons" if Evans brought his own "chicken's teeth and penguin feathers," though this line of dialogue wasn't ultimately used in the episode.