Yes, I know it’s Gene Roddenberry in our world, but in the TOS episode The Man Trap, Sulu says this to Yeoman Rand:
“May the great bird of the galaxy bless your planet!”
You can see it in this clip: https://www.youtube.com/watch?v=lk3tM4Ns3LY
There is also this Okudagram that appeared in two TNG episodes (The Naked Now and Conspiracy) and was clear enough on-screen to make it less than just a joke:
So it appears that there is something known as The Great Bird of the Galaxy, it has a human head, possibly a Starfleet delta, and it’s used in a saying that may or may not be an actual blessing.
So what was it? Was it an Academy joke? Was it a real religion? Obviously it was more than just something Sulu made up since there’s an entry for it on the Enterprise D’s computer (which seems like an odd thing to have if it’s an in-joke).
I messed up and deleted the wrong comment. Sorry about that.
Original content: I think it likely that it is some kind of near deity like the christian god, or the Klingon gods that make an appearance. Not to mention the Koala.
I can’t head canon the TNG images as there’s a lot of “hidden” filler stuff that’s been found that doesn’t make sense and are inside jokes. But I could rationalize Sulu’s statement based on some of the background created in novels with his family history, cranes and such, and maybe he’s extrapolating it. The early episodes were not the best to use for canon stuff anyway, as they hadn’t figured lots of things out yet. Have we ever seen sentient plants since this?
I agree, there are a lot of inside jokes. This, however, was, as I said, clear enough on screen to count as more than that.
Here it is from Conspiracy:
There’s an entry in Memory Alpha with a few other references, one being Peter David novels where it is an actual creature.
Unfortunately, they don’t give any more information than I have already given, aside from the Peter David novels, which aren’t considered part of Star Trek canon.
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The Koala is apparently also canon since an omniscient being said it was there and Boimler saw it during a near-death experience.
Right. I think the real question is: How did Sulu know about it? I would love to believe that it was formless and Sulu just had a wacky belief, and upon hearing it said out loud it thought “LOL, OK then.”