The prompt was:
In the movieverse, the cube was used for new life and healing. What if the all-spark had only dislodged Megatron from his body, not killed him, as it was unable to kill something. It almost self-destructed trying.
Megatron really needs to get fixed to get back in his body, but even if he took over Ratchet he wouldn't be able to use his skills. He therefore takes over some poor mech (author's choice) and forces Ratchet to heal him. Of course, he can't hurt him physically or mentally because he needs him to do a good job. However, there is another way of bending others to your will. The kink is possessed sex, with Ratchet knowing that the person is possessed, therefore unable to hurt them.
Megatron was never the most religious of mechs, but when he saw the fleshling charge at him with the All Spark in his squishy little hands, he honestly prayed for a respite. Luckily for him, and unfortunately for the Autobots, Primus must have loved him for he was able to online his optics. A movement to his right caught his optic. Ratchet, his processor supplied, the Autobot's CMO.
Snarling, he thrashed on the berth, trying to escape from the enemy's medic before he was slagged even further.
"Jazz! Jazz, calm down" The medic was running over "Listen to me, you're not in a battle anymore."
He stilled his motions, processor whirling. Jazz? Ratchet took the opportunity to stab a needle into his energon line at the base of his neck, and Megatron's world went black.
Ratchet sighed, looking at the sedated form of his friend. At least he would be onlining in a few breems now – for a few terrifying moments in Mission City, he thought he had lost the little fragger to Megatron when he was ripped in half. Ratchet was truly amazed and relieved to find a small ember of spark nestled in Jazz's spark chamber, and immediately set about patching the two halves of Jazz together. And two weeks later, Jazz's chassis still looked like slag, but it was mostly cosmetic damage now. All that was left was his visor, but that had to wait until they had more supplies.
With a slight bounce in his step, Ratchet went back to sorting his tools, waiting patiently for Jazz to online again.
Megatron's processor booted up first, but he did not online his optics. He quickly went over the situation at hand – the medic had called him Jazz, did that mean he was in that slagged mech's body that he tore in half? A quick query sent to his database confirms his suspicions. And sweet Primus, he found codes for access to most of the Autobot's files. If he wasn't trying to keep the medic from noticing he was online, Megatron would have cackled in joy.
As it was, Megatron found that he could call upon all of the personal memory files that Jazz ever filed away, and decided that he was indeed in total control of the saboteur's body. He ran through the basics schematics of the body he was in. Mmm, a highly sophisticated stealth system, although Megatron was rather disdainful of such small builds. He preferred large frames that screamed power, but maybe it was prudent to act as Jazz for the moment, at least until he had gained his bearings and gotten a grip on the situation. Megatron was not stupid, despite what Starscream always claimed. A light touch on his right servo had his optics snapping online. Show time.
Ratchet retreated after lightly tapping on Jazz's servo, he knew when Jazz came online a few breems ago. He was relieved that his friend had not reacted violently again, but it never paid to be too careful. The CMO watched cautiously as the silver mech sat up, rubbing his helm.
"Ratchet?" Jazz asked, a touch of hesitation in his voice.
Ratchet broke out into a broad smile, and closed the distance between the two mechs, sweeping the smaller Jazz into his arms in a tight hug. He was normally not one for such emotions (he had a reputation to maintain, after all), but it was times like this after a particularly complicated repair that he lost his desire to snipe at his patient. He loosened his hold on Jazz after he felt the other mech stiffen in his embrace, but kept his servos on his shoulder.
Megatron was not used to mechs randomly touching him, so Ratchet's embrace came as a complete surprise. But, something at the back of his processor welcomed the touch, the warmth after vorns buried in the snow and frozen in the fleshling's stupid facility. The low rumble of Ratchet's engine was quite soothing, truth to be told. Just as he was starting to actually enjoy the medic's deliciously warm chassis pressed against his own, he was pushed away and held out at arm's length. He almost protested, but managed to silence his vocalizer in time.
"Ratchet? What happened?" Megatron did not have to fake the touch of confusion that crept into his voice. He was genuinely curious about how he came to be in Jazz's, of all mech's, chassis, and if anyone could enlighten him here on Earth, it was the slagging Autobot's CMO.
Ratchet was surprised that Jazz had dropped the human vernacular that he'd been using since they arrived on Earth, but dismissed it in favour of filling Jazz in about the battle at Mission City, transmitting a short data file on what happened. Jazz's optics flickered as he accessed the file, and Ratchet turned away to grab a cube of energon, fresh out of the newly built dispenser on the other side of the med bay.
Megatron winced as he watched his own self being destroyed by that Primus-damned organic, watched as his body was unceremoniously dumped into an abandoned warehouse near the edge of the Autobot's base, awaiting disposal into the sea. But a medical subroutine in Jazz's processor told him that his body was not slagged beyond repair yet, and that body was laying barely a click away from the med bay. Megatron smirked – he knew he was probably looking at the only mech who could put his body back together again. It was nice to know that Primus was still smiling down on him.
Raking his optics over the 'bot's rather shapely aft, Megatron could not believe his luck. He was going to blackmail his way into getting his body back and reclaiming his place as Decepticon leader, and he was going to have fun doing it. Oh yes, Megatron could imagine it now, his smirk widening, fragging the medic senseless was definitely on his to do list. He could consider it payback for what that pesky former Senator did to hinder his progress back on Cybertron. And Prime could go wallow in jealousy, if the saboteur's memories were to be trusted.
Megatron carefully scanned the body he was in for any signs of the dead Autobot, but there was no trace of Prime's second in command that showed up on his scans. Well then, it was time for a little lying.
Ratchet turned around, two cubes of low-grade in his servos, and stopped short. The SIC was staring at him with a smirk on his faceplates, only it seemed vaguely sinister. He shook his helm, as if to clear it, and approached Jazz, not missing the way the smaller mech's optics tracked his every movement.
Handing one cube to Jazz, Ratchet offered, "Glad to be back in the world of the living?"
"Oh, you have no idea," Megatron accepted the cube from the medic, and relished the smooth flow of energon down his tubing, not taking his optics off the chartreuse mech. He could not wait to see the shock on the pretty medic's face once he told him who he really was.
Ratchet was starting to feel a little uneasy on the lack of questions Jazz had on the death of Megatron and the destruction of the All Spark. Maybe it was just the shock of seeing his body torn in two by the Decepticon leader, Ratchet told himself, but deep down in his spark, he wasn't convinced by the answer himself. He pinged Optimus to let him know Jazz was online, but was to have no visitors until he could verify his mental health, and Prime acknowledged with an answering bleep.
"Well then, I'm sure you must be glad Megatron's off lined permanently," Ratchet began, "But you should…"
He stopped midsentence as he caught sight of Jazz leering at him. His processor almost frizzed. That expression on the silver mech was one of the creepiest things Ratchet had ever seen. The most creepy thing would have to go to the way the SIC was stalking towards him, seemingly filled with a taller, stronger presence. Ratchet started backing away from Jazz, trying to put as much distance between them.
"Are you sure about that?" And holy Primus, that was definitely not's Jazz's voice coming out of the vocalizer. That low baritone voice…
Megatron felt a pleasant tingle run through his circuits as the medic's optics widened in recognition.