Robo Dune
Herb really liked Dune, so he made a planet just like it. In the beginning it was just an amusement park costing something short of a quadrillion dollars, a rough estimate at that. As the colossal project went into development and years went by, people forgot what it was supposed to be and simply started living in it.
His name wasn't Herb, of course. He changed that. But what does it matter what his parents named him? Herb was his true self. A genius, a lunatic, as one doesn't exclude the other. On the contrary, they usually go side-by-side.
Herb made roboworms, since he couldn't genetically engineer living ones no matter how much he tried. Oh, he tried, and the dunes are literred with the rotting carcasses of his failed experiments. Giving up, he simply made them robotic and decided to be done with it. That way they would be easier to control, anyway. The spice melange was the easiest one to make, simply a mix of hallucinogens and a banned military formula for supersoldiers mixed together. That, fabricated inside the roboworms, since they were giant, mobile, automated manufacturing plants, gave the Fremen all the abilities from the Dune mythology.
Herb made encampments on rocky grounds, he put humans there that had to scavenge the moisture to survive in the unforgiving desert, and he placed a palace so that the park's visitors could have breaks of luxury and comfort.
It all worked well, until the trade routes broke down. Isolated, Dune carried on existing. Generations after that, the people believed as holy gospel what their theme-park instructions were. The Fremen awaited for Muad'Dib, their Messiah. Their lives were hard in the harsh environment, their generations were short and ever-replenishing. When every day is a struggle for survival, religion, especially a manufactured one, becomes an easy thing to believe in. To hope with.
The Fremen forgot they were entertainers and simply survived.
The Atreides liked their royal bloodlines so much they casually forgot how someone had just hired their ancestors to perform that job. They were simply better actors, that was all. With a bit more charisma and gravitas, to sell the whole Dukedom to the wealthy visitors looking for an authentic experience. It was much easier to simply go full-method on their acting and live the part every minute of every day. It wasn't a bad gig, they had servants, they had power on the desert planet, they had armies to command.
After a couple of generations, they simply stopped acting and started living their new roles.
As for the psychic powers? Good question, but that was the easiest one to implement. Herb mulled over the issue many years before even pitching his colossal project to potential investors. He came up with simple devices, pure technology, nothing magical at all, that could replicate the telepathic effects, the Voice, everything. He simply injected nanobots into the actors and gave them powers. Anyone of equivalent technological level could have detected them and blocked them entirely, but the employees of the original theme park were from a less-advanced planet.
The early ones knew there was nothing magical about their powers, they even read instruction manuals on how to use them correctly. But the later generations forgot about that, and accepted the powers as something genetic, something only they possessed. In part, that was accurate. Only the descendants of the original actors had the necessary nanobots to use the telepathic powers. So, in a way, their belief in the bloodline was real.
And what is this casting for, you ask?
Well, every good story needs a villain. Every epic story needs an epic villain. You fit the part of Baron Harkonnen, we're gonna need you to audition for the evil laugh, the maniacal one, yes.
And we're gonna need you to gain a few kilograms, but that one can be arranged easily while you train.
What? Yes, we will have to put a plug on your heart, sorry, those are the rules.
The floating? The antigravity harness is a trick with superconductors, it just works, we've tested everything thoroughly.
Yes, you will have to be evil. And take over Arrakis. And kill a bunch of people.
Oh, so eager.
Right.
Sign here in triplicate, please. Once you do, you will follow me for the mindwipe and the memory implant procedure down the hall.
What? No, you can't meet Herb. He is long dead, his estate carries on his wishes and runs the theme park.
Yes, your current self will be erased, unfortunately. But hey, you get to be a Baron, right? How cool is that?
The End.