Here's the original introduction used for Star Trek's second pilot, Where No Man Has Gone Before. This intro (as well as some other elements) were later edited/removed when the series was green-lit for production and had to meet the then-standard 50-minute time limit. The removed footage was long-thought to be lost, but was recently rediscovered by a German film collector and made available on the Season 3 Blu-ray release of TOS. The existence of this 'alternate version' of the second pilot has been known to fans since before series actually premiered (and low-res VHS dubs have been floating around ever since), as it was shown at a conference only days before the first broadcast episode, The Man Trap, hit the airwaves.
Anyway, enjoy this little piece of early Star Trek production history!