I have NO IDEA where this came from. It's... weird. :-P
It started with strange symbols dancing before his eyes. Golden lines of light that told stories in a foreign language that he somehow understood.
Lives played out before his gaze. His grades fell steadily as his ability to pay attention to the outside world diminished.
“I don't understand,” he vaguely remembered hearing his mother say as she pressed a cool hand to his forehead. “He's not sick. He's perfectly healthy... Ron, what's happening to our son?”
He remembered Bumblebee asking after him, and his own swift brush-off. “I'm fine, Bee. Just... Eh, teenage angst, I guess.”
His guardian had only given him a worried look.
Days, weeks, months, passed in a blur, with only the golden symbols holding his attention.
He was in class when he heard it. A tiny, quiet voice, whispering in the back of his mind. Giving him the answers, changing the way he thought. It was strange... but, at the same time... hadn't those glyphs been doing the same thing to him for... almost a year, now that he thought about it.
It felt surprisingly natural.
So he continued drifting, brushing off the concerns of his family, his friends, his guardian.
Until, one day, Bumblebee had enough. Instead of driving home one day after school, he headed toward the desert. Sam didn't notice until they were already a couple hours out.
“Bee?” he said sleepily, blinking at the passing sands. “Where are we going?”
Bumblebee took a moment. Then, a short snippet of lyrics drifted from his speakers. “Doctor, doctor, gimme the news.”
“Going to see Ratchet? Why? Is something wrong? Did you hurt yourself?”
For a very long minute, Bumblebee mourned the fact that his charge had grown so distant. His vocalizer had been fixed months ago. Sam never seemed to remember. Never asked why he didn't speak, and if he did speak, asked something like, “Where did you get that clip, Bee?”
So he pulled up another clip. “What's your problem? Can't you see it?”
“Me? Bee, there's nothing wrong with me. I’m fine.”
He sounded fine. But there was a strange light in his eyes. A distant sort of fogginess.
So he said nothing, simply drove on. Sam tugged at the wheel once, then left it alone and simply gazed into the middle distance for the rest of the trip.
He “woke up” again while in Ratchet's Med Bay. The red and white medic was shaking his head. “There's nothing wrong with him, Bumblebee. Nothing physically, at least. Whatever it is that's making him act like this... I can't help you. I’m sorry.”
And Bumblebee, dejected, picked up his charged and went home.
It was close to a month later that Sam noticed the stiffness in his neck. He ignored it. It was irrelevant.
The stiffness didn't go away. It spread, down his back, through his arms, down his legs, until his whole body felt stiff and un-bendable.
Some time after that, he noticed the long streak of silver on his arm. He poked it. It was hard. Metal.
That little voice was back again.
He just put on a long-sleeved shirt and continued on.
I wasn't lost, the voice whispered. I'm in you. I am you. You are me. You will be me.
Why? Sam asked.
The voice didn't answer.
The metal slowly spread over his whole body, leaving his face and hands covered in skin, but he could feel the metal under it.
It is almost finished, the voice said one day.
What is finished
Me, it answered, and would not say more.
Bumblebee brought him back to Ratchet. This time, Ratchet did find something wrong.
“His body is almost entirely made of metal... How did you not notice this, Bumblebee?”
Sam knew it was because he was shielded, somehow, but he said nothing. His guardian shook his head, optics wide. “I don't know, Ratchet!”
They kept him on the base, in the Med Bay. He wasn't allowed to contact anyone but Bumblebee and Ratchet.
He curled into a small ball and stayed there. He didn't move, didn't think, didn't do anything but lay and listen to the voice and read the glyphs that still filled his vision.
He heard their worried voices, but did not think much past hearing them. He saw with unseeing eyes as they frantically tried to find out what was happening to him, but did not register their panic.
Slowly, he felt himself disappear. The voice took his place, merged with him, became him, and he became it.
It was always destined to be, it said. I am you, and you are me. We are one.
And, in a flash of power, Sam was gone, and AllSpark was in his place, but Sam was still there, in the deepest parts of what made AllSpark what it was. And he made his frame into something more suitable, a geometric shape, a cube, lined with runes and light.
And when Ratchet came rushing into the room, alarms all blaring, he did not find a small, metal human. He found a Cube, the AllSpark, sitting peacefully on the berth where Sam once lay, sparks dancing off its edges, lightning flaring off its sides in short, bright bursts.
The AllSpark felt the scan the medic ran over it, then watched as the medic left the room, then returned with the Prime.
The Prime! A true Prime, after so long floating among dead stars and planets and then the fleshies who didn't know their Primes when they came. A flare of power stretched out to brush the Prime's spark, and Optimus staggered to a halt.
“Primus,” the mech whispered, optics wide.
The AllSpark flared again. It was back. It had new understandings, from what it had been before, the human, Sam.
It was back, and stronger than it had been before. The Cybertronian race would not perish. The energies that made it up could not be destroyed. They would simply find a new host and make it suitable, and all would continue as it had before.