^And that's what they would've done if they'd had more money. This was a low-budget show. The networks were reluctant to go for it at all, fearing the expense of creating alien worlds. Roddenberry's "parallel development" conceit may have been an absurd bit of science fiction, but it was a brilliant piece of marketing, because it gave him a clear, high-concept "hook" for selling TV executives on the idea that the show could be affordable. If he'd said "We'll use existing backlots but dress them up just enough to look alien," it would've sounded more complicated and expensive and wouldn't have been as straightforward a sales pitch. It would've raised questions about just how much redressing would be necessary, and overcomplicated the sale. But by saying, "We'll have exact parallel worlds so we can build a story around leftovers from any period piece or contemporary drama," that's going to sound good to the penny-pinching executives.
(You know, come to think of it, it's amazing it took them until the third season to do a space Western.)
(You know, come to think of it, it's amazing it took them until the third season to do a space Western.)