MAN TRAP was the first aired episode, and yet from what I have read, six were in the can. Many point at that premier episode as being one of the reasons TOS had a bumpy start. You know what they say about first impressions...
Of the episodes that were in the can, which one would you have gone with first?
I've always wondered about that choice myself. If only Star Trek had had a different opening episode, the show might have made it out of its first half-season instead of being a flash in the pan barely remembered by a few fans...