The four founding worlds of the United Federation of Planets are Earth, Vulcan, Andoria and Tellar. Everybody knows that. But we didn't actually know this until Enterprise season four!
Brannon Braga called Mike Sussman for a quick question, hey, who were the founding members except Earth and Vulcan? Sussman, who was a real Trekkie, and also a writer and producer on Enterprise, had to make a decision:
> What flipped through my mind was that it had never been established, but there had been a lot of fan speculation going back to โJourney to Babelโ that many of those races โฆ were among the founding members. For that quarter of a second Iโm thinking, โWhat do I tell him? If I say itโs never been decided, he might make up a couple of new races and that might set certain people off.โ So I basically lied to him and said, โOh yeah, itโs Andorians and Tellarites.โ He put it in the script and now itโs canon!
TIL.