It's the fish. The show's about the fish. Those fish in the tank in the middle of the room during all of boom? They, not Jules and Jo, are who survive the end of the world as we know it and evolve into the next evolution of the world.
That was a huge spoiler. When/if you head up to Next to see the show, it will have, in effect, been 'ruined' for you. Normally I would consider apologizing, but believe me, you're better off that way. The show, about two loners in their own way stuck together after an extinction level event, nibbles on the idea of both the futility and the struggle of making a true connection with other humans and the wonders of the simplicity that actually becomes that intimacy. And the show is ultimately a very conflicted (in a promising way) tragicomedy -- a silly 21st century romp in which two virgins are left to people the new world but are too incompatible to do so, yet when they finally fall into each other and decide to brave this new world together, they die within minutes -- still virgins. But Peter Sinn Nachtrieb has decided to mask the tragi- part of the tragicomedy as a half-telegraphed bullshit surprise twist that takes all semblance of actual substance out by the knees and replaces it with "Did you see that coming?" frivolity.