Automation

You are Gear, and you've just been given what might be the best birthday present ever! It's a brand-new type of VR headset: not clunky like the other ones on the market, but a lightweight, narrow curve of transparent green plastic that sits right in front of your eyes.
You've never even heard of a VR set like this before, but your friends are telling you about how it bounces images right into your eyes. Or something. It sounds too good to be true.
Not really listening to the technical explanation, you slide it into place with your hooves, and immediately a display comes up with some startup information as you look out at the world through a field of nearly transparent green.
For a few minutes you simply watch meaningless technical information about 'ocular receptors' and 'drone configuration'.
Just as you are starting to get well and truly bored, you suddenly notice an anomaly: a blue streak snakes out from the center of the display, curving around itself, getting further and further from the center.
You start to tell your friends that it seems to be broken, but they seem to have noticed, too. They simply watch you. One of them chuckles, while another squirms as they watch.
But even though you try to look at them, to find out what's going on, you can't. Your eyes are dragged back inexorably to the center of that swirling color.
As you stare at the spiral now filling your vision, it seems as though there is nothing to worry about. You do not need to be worried. You should just relax. Obey.
The last word almost reminds you of something, before it is washed away in a sea of contented feelings. All your friends are sighing with relief for some reason. They look somehow... eager?
Eventually, they all turn and begin trotting in the same direction: into the basement of the building they booked for your party.
You follow along at the rear of the group, not knowing why, but knowing that you must.

You are standing at a door leading into a room marked 'Processing'.
Nearly all of your friends have gone somewhere else, and you haven't seen them since.
It's nearly time. For what, you don't know, but in spite of yourself, you feel a sense of excitement.
Then one of your friends trots up beside you.
You know this pony, but part of your mind is filled with a sense of unease at the sight of her.
Then a strange feeling you can't determine the source of flows through your mind, washing away those feelings bit by bit, like the tide washing away a sand castle.
You stare at the pony, as those feelings of unease are gradually replaced with feelings of affection... then of longing. You can feel yourself getting moist just looking at the cute pony.
'No!' a part of your mind tries to tell you, 'She's doing something to you! To all of you! Snap out of-' and then the internal voice is gone, and you are staring into the pony's eyes from behind your visor, and all you feel is a warm feeling between your legs and a desire to do whatever she commands.
The pony leans in, a triumphant sneer on her face. "Happy first birthday."
Her words mean nothing to you, but her muzzle so close to you nearly pushes you over the edge.

Then it's time to go through the door.
You step inside, and immediately machines begin to whir around you.
You barely register what's going on, but you feel yourself being turned somehow into metal.
Not all of you, though.
Your legs are first, followed by something that feels like a metal saddle, then something at the back of your neck, like a metal collar.
Your moist pussy is left organic between metal legs, and you feel yourself dripping onto the floor.
When everything else is in place, two antennae, like the ones on robots in anime, come down on mechanical arms and fit themselves to either side of your head, connecting with the visor. As they do, the swirl you had ceased to notice stops, and for a moment, you feel almost like your old self again.
It feels like you've just woken up, but are still muddled by sleep.
Then there's the 'click' of something inserting itself into the metal on your neck, and new thoughts flood your mind.
Not thoughts, but... programming.
For an instant, you instinctively try to resist, but the first bit of programming instructs you not to resist. To accept your reprogramming. To obey.
You do.
As the rest of the commands come pouring into your processor, you find yourself imagining the pony outside, now with words like 'Mistress' and 'Obey' indelibly associated with her in your mind.
Each of the ponies at the party appears in your mind in turn.
With each one, data flows from the machine and into you, overwriting your free will, programming you for your new and better life.
More of you is transformed into wonderful machine while you stand there, absorbing commands.
As the information flows into you, you feel your still-organic lower bits build to climax, and before you can even try to stop it, you orgasm all over the floor and your shiny new legs.
It happens several more times as you are reprogrammed, although you stop feeling any sense of shame after the first.

Eventually, you step out and see your Mistress, waiting with the other ponies from the party.
You stand before them, awaiting instructions, as is your duty.
You listen dutifully as you are assigned your task.
You are a pleasure drone. This pleases you greatly. Any assignment would please you greatly.
You live to serve Mistress.
You exist to obey.
These ponies will use you.
Your remaining organic parts will bring them pleasure.
This is one of your purposes.
The other, though it is not said, is understood: you will aid your Mistress in secret.
These other ponies, the erect stallions and the eager mares, will be changed as you have been.
You will pleasure them sexually, and then bring them the ultimate pleasure: conversion and servitude to your Mistress.
They will become obedient machines, just like you.

Today is the first birthday of your new life as a mindless drone.