The Great Bird of the Galaxy was a mythological creature evoked as a blessing. In 2266, after Yeoman Janice Rand brought him some food, Lieutenant Hikaru Sulu said "May the Great Bird of the Galaxy bless your planet!" (TOS: "The Man Trap")
Background information Edit
The Great Bird of the Galaxy was the nickname of Star Trek creator Gene Roddenberry, given to him by associate producer Robert Justman. It was used in the original series as an inside joke. (Star Trek Encyclopedia 2nd ed., p. 178) The "Great Bird of the Galaxy", according to Peter David, is actually a giant bird, and appears in the Star Trek: New Frontier novels.
An early Okudagram was later created during TNG Season 1 that depicted an image of the Great Bird – Gene's face placed on the body of a parrot wearing a Starfleet uniform. The Okudagram was based on a full-color painting Andrew Probert made, as gift for Roddenberry's sixty-sixth birthday in 1987. (Star Trek: The Next Generation 365, pp. 130-131)