There are many in-jokes that people have added to displays and scripts for Star Trek over the last 50 years. Examples include: * the recurrence of the number 47 * various displays on okudagrams and indeed the name okudagram itself * references in the Star Trek universe to other science fiction shows and movies * references to real world facts about other Star Trek series (Camus II) * the "sharing" of planets and species between Star Trek and other science fiction * nicknames for production staff or crew making it into references within continuity (see: great bird of the galaxy) and so on.