Okay, first of all, if you haven’t seen The Dark Crystal go see it. I’ll wait.
Did you see it? Good. Let’s continue. So Kira and Jen are the last two Gelflings, as far as they know. And they save the world from the Skesis, heal the crystal and that, but who cares? At best they can have kids themselves, but then their kids are fucked. Unless there are at least 20 other breeding pairs left, or incest doesn’t result in goober babies on crystal world. The Dark Crystal isn’t the only movie that has this problem. I can’t think of any others at the moment, but I know I’ve seen them. Some one is the last of the somethings and then they find THE OTHER ONE. So they don’t have to die alone, I guess… There really needs to be something that adresses this problem in storytelling. Can it really have gone this long without anyone thinking of this? Actually no. I already know of a bible story where they adress this very problem. When Lot, and his family, escape God’s wrath visited upon Sodom and Gomorrah his daughters think they are the last people alive and trick him into fucking them so they can have kids. Whic genetically isn’t that bad. The web toed kid thing from first cousins is actually a myth. As long as you don’t KEEP doing it the chance of doodle kids isn’t much worse than random chance. If you keep it up the weak genes start to double up geomertically and then everyone is fucked. Like royalty.
As an aside, in some ways tyrants are stymied by their insatiable desire to fuck cousins. Eventually the family line gets so backwards they become unfit to rule and the peasants can oust their cousin humping asses. The British royal family has gotten wise to this, however. Truly they are the cleverest of kings. Also, I guess countries where they have harems get past this too. The harem is kind of what evolution wants any given man to achieve. Sex up as many women as you can so your specific code gets out as far as it can. You can kill off as many rivals as you want so long as you leave enough for your offspring to get down on. Kings that throw dick wherever they like are the ones who win genetically speaking.
Anyway, whoever is responsible for that bible story already figured this whole “last of our kind” problem out and adressed it, but we seem to have abandoned that wisdom. I’m not saying you have to show other survivors of decemated races, but you might alude to rumors about sightings or something. That was one good thing about The Secret World Of Arietty. They suspected, at least, that there were still other borrowers out there. Then one showed up. Maybe not the best choice for a mate, but Arietty won’t have to safety dance all up on her pa.
In Fraggle Rock, before I saw the later episodes, I thought the Gorgs had this problem because there is no evidence that there are other Gorgs. Eventually you find out that there are, and that the Gorgs you see in the show are FUCKING DELUSIONAL. They aren’t the king or queen of anything and Junior eventually will be able to find a mate. I don’t know how Henson forgot that whole deal between Fraggle Rock and Dark Crystal, but he also forgot about doctors and kind of made it impossible to ask him.
You know what else is odd about Fraggle Rock? You never see Fraggle kids. The Doozers had the whole range of ages, but Fraggles only had teens to the aged. They implied that Fraggles do procreate, but you never actually saw baby ones. I can’t imagine a Fraggle being a very responsible parent, but there were certainly a lot of them. They must have had some kind of care system, or something. I guess there had to be other Boober-esque Fraggles who actually enjoyed tedious tasks, like child rearing. Or maybe they just stuck the babies all in some pit so the strongest ones would survive.