A/N: This is an answer to a challenge on LJ, 'accidental stimulation'. The site hates me and keeps crashing, so it's gonna be posted here. This is only a one-shot and written purely for entertainment, it is in no way related to my story Intertwined.

Warnings: Slash! This has smut between Optimus and Sam. Pretty much that, since this is only a one-shot.

Summary: Sam is experiencing a side-effect from one of Ratchet's experiment gone wrong. Now he has rather vivid dreams involving Optimus, and Mikaela wants to have a sleepover with the giant robots…

Dreams

Mikaela had been the one to propose the brilliant idea of them having a slumber party with the autobots. They couldn't exactly invite them to either of their houses, so they were having the party at NEST headquarters, which was a place where everyone could fit inside. Unfortunately, Sam had been exposed to one of Ratchet's more unusual experiments, and one of the side effects was rather…vivid…dreams.

The dreams were rather intimate, and that would be fine if it was Mikaela he was dreaming about. No, instead he was having dreams where he was on his back and a certain autobot leader was doing very pleasant things to him. He just had the luck that Optimus wanted to talk to him and had opted to let Sam sleep on his seats in order for there to not be any inconvenience. Sam couldn't exactly say no, the prime had given his life to protect him so he couldn't snub him for no apparent reason. Just because he had died for the prime in return didn't mean he had the right or want to do that.

Now he was sitting in those comfortable seats that molded to his body perfectly, like an embrace, and he felt a blush come to his face at the thought. They had already gotten the pleasantries aside and Sam desperately tried to rid himself of his flushed skin before Optimus' sensors picked it up and he started asking questions. It was too late though, as he felt the warm blue light coming from the sensor in the dashboard send tingles down his body. It was different than Ratchet's scans, which felt like a sleeping limb coming awake and caused him to squirm uncomfortably, or Bumblebee's, which tickled a lot; no, this was…pleasant and he felt even more heat rush to his face before the scan was finished.

"Are you alright, Sam? My sensors show that your skin has warmed but I am detecting no irregularity in your internal systems other than a quickened heartbeat…" Optimus said, with his deep voice rolling from the speakers of the radio and Sam shook his head to clear it.

"I'm fine, just a bit tired, what did you want to talk about?" Sam asked as he forced himself to calm down by just relaxing into the seats and enjoying the comfort with enjoying it too much.

"I wanted to apologize for Ratchet's actions last week. If I had thought to warn him sooner about experimenting when humans were near you never would have had those chemicals land on you…" Sam could remember the burning liquid landing on him, making it feel as if his skin was melting before it turned soothing and pleasurable and then disappeared completely. Ratchet had scanned him after removing any traces of the chemical from his system, but it had done nothing to him really. It had been in just its beginning stages, so no harm came, just his weird side-effect, so Sam wasn't really mad.

"I'm not mad at him or you; there was really no actual harm done and he was just trying to find a cure for something, right? There isn't anything wrong with that. The whole thing with it landing on me was an accident." Sam replied hastily since he didn't want Optimus feeling bad.

"You have been avoiding NEST lately and I had thought it was for that reason." Sam shook his head and patted the seat he was on.

"No, I've just been busy with school. I'm sorry," He said, hoping Optimus couldn't hear the lie in his first sentence. He was sincere about the second though, because he was sorry for avoiding them because he was embarrassed and he was sorry for lying just now. Optimus paused before he started asking how school was and Sam relaxed as he complained about his asshole Astronomy professor and Simmons (who kept calling to chat) and Leo (who he, Sam, kept having to stop from revealing where the autobots were).

He didn't even notice when he had fallen asleep.

The chill of the floor beneath him didn't bother Sam as he looked up at the prime in front of him. Electricity of the most brilliant blues swirled in a chaotic dance from Optimus' spark chamber and Sam smiled as he reached for the spark, a moan escaping him as smaller sparks broke away from the main and started dancing along his skin in their chaotic, pleasure inducing patterns. Ignoring the urge to collapse and let the sparks work their magic, he stood and allowed Optimus to scoop him up, indulging in the cold flush of metal against his heated skin as the approaching spark got closer. He listened to the whirring of gears and the groaning of metal as Optimus sat down before lying on his back and placing Sam right below his spark chamber.

Sam caressed the opening of the chamber, this section of metal heated against his skin, and grinned at the sounds the robot made. He leaned down and kissed along the edges before he slowly reached for the spark, and gasped as the energy ran through him, flooding his very pores with pleasure. The whole world seemed to fade away as Optimus became the only thing he could focus on. The humming energy flowing around him, the vibrations against his cock from the metal plates covering the engine below him, and the feel of Optimus' hand as it held him close with the sparks of energy gathered around it crackling in the air as they intensified their pleasure… The sparks traveled down the length of his body, leaving trails of tingling pleasure before they teased his cock and entrance, and he came. Sam's orgasm racked his body as the metal body beneath him heated up and he could barely hear his moans at the sensation as he fell into darkness.

Gasps escaped Sam's form as he was swept away in his dream, quiet moans leaving his mouth as he rubbed against the seats embracing him. It was a subconscious movement that the boy was unaware of as he thrashed against the leather to get the friction his pulsing member desired.

Optimus had already slipped into stasis, but the sensations he could feel from the boy he protected… He didn't want to wake his charge since he didn't want to disturb him and have no reason to say why other than it was making him feel…aroused…yes, that was the word humans used. Sam would not accept that, so he forced himself back into stasis as a single word escaped Sam's lips, "Optimus…"

Optimus looked at the small being before him and felt his Spark hum against the plates of his spark chamber, the energy trying to reach the human. It was unusual for it to feel called to another being who had no spark for it to merge with… No, Optimus felt that it was he, himself, who felt called by the beautiful boy before him and that it was such a calling it affected his very Spark. He kneeled and gently cupped Sam with his large hands, enjoying the feel of such soft skin against his metal, before he lifted the boy closer to his face to better examine him.

He was so very fragile with his soft skin, those warm brown eyes that could easily be pierced, and bones that broke too easily… But he was so much stronger than many of Optimus' own species. He had given his life to save another so his race would live, he had fought against beings he knew could kill him in one hit, and he had trusted a race so alien to his own with his very life. Sam was a very beautiful boy and a very brave warrior, so Optimus made his decision.

He pulled the human closer and felt the soft hands trace his facial components before something warm and wet touched his lips and Optimus wondered if that was a kiss. It was…unusual, but still pleasant, and he smiled as best as he could. He traced a finger along the human's spine as he opened his spark chamber and the light came rushing out. It enveloped his human, who moaned in pleasure, and he could feel every sensation Sam was feeling, which caused some rather inappropriate Cybertronian language to escape his vocal processors. He laid down and rested his human on top of him and Sam seemed to know exactly what to do as the Spark thrummed in it's chamber, fragments of it dancing along Sam as the boy started reaching past Optimus' armor to more intimate spots.

Primus, he loved that Sam's hands were small enough to fit in such places as the boy grabbed a wire and squeezed. The nerve wires coded for pleasure were hidden quite well so that, in case of battle, no bot would suddenly be thrown into ecstasy, but with the concentration and openness during a Sparking they could be reached. The soft hands rubbed against that one wire insistently and Optimus could feel his systems heating up and he cupped the human close, wanting to be holding him so that when Optimus offlined the boy would be safe.

His visual system flickered as the heat of his body grew and he could hear his cooling vents working frantically, but it was no use as Sam willingly placed his own hand in Optimus' spark and he felt pleasure flood his circuits. Then everything went black as he offlined.

Sam woke up at the intense heat in the cabin and he blushed in embarrassment as he noticed the wet spot on his sweats, but luckily the heat had dried the cum and none had leaked onto the seats. More worried about his friend, Sam sat up and looked at the dashboard to see the controls going crazy, but when he was about to say something as he frantically ran his hands over the leather to check if anything was wrong, everything stopped. He watched in stunned silence as everything came back online and he wondered if he should draw attention to himself when Optimus didn't say anything. As cool air started flooding from the vents he decided not to and instead sat there and watched the sunrise through two windows, Optimus' and the window of the building.

When Mikaela suddenly knocked on the door, Sam jumped and he thought he felt even Optimus jolt a little, and he quickly covered himself with the blanket he had brought last night. Pretending he was just cold, he opened the door to see his smirking girlfriend. "You have fun last night, Sam?"

"Wh-what are you talking about?" He asked, failing to hide his nervousness. He moved the blanket to wrap around him more in an effort to hide his stained pants.

"The window was cracked a little to let air in before someone closed it to muffle certain moaning sounds," She taunted as she pointed at the driver's side window, which was now fully closed. "Did you have a nice dream?"

He glared at her smirk and stepped out of cab of the truck, walking over towards his bag in an effort to ignore her. "So, was it about me or a certain au--" He didn't even remember moving, but his hand was covering Mikaela's mouth to stop her from saying anything. He had confessed to her the nature of his dreams and she had been fine with them, but she teased him endlessly and sometimes he wished he cold just get over his embarrassment. Then he could officially break up with Mikaela (they had decided to break up after the first dream, their relationship was just a cover) and tell Optimus how he felt since he had always had feelings for the leader, they were just revealed by Ratchet's chemicals.

"Don't say it and I'll move my hand…" Sam said and she rolled her eyes before nodding in agreement.

"They already know…" She whispered into his ear and he felt his eyes widen. How could they have possibly known? Was he shouting Optimus' name? "…Optimus had a reaction; Ratchet recognized it as a sparkdream, which is their equivalent of wetdreams."

Sam looked over at the prime, who was transformed now and being talked to by Ironhide, his closest friend, and Sam watched with dread as Ratchet approached him.

"Sam, if you wish to be spark-bound with Optimus, you should read this." The medic said as he handed him a stack of papers held together with staples. They were still warm from the printer and Sam read the title: Guide to a Safe and Pleasurable Sparking, by Chief Medical Officer Ratchet. He felt his face heat up as ratchet handed Optimus a stack of papers as well and his eyes caught the blue optics of the autobot leader. He smiled shyly and was happy to see Optimus nod in return.

Perhaps loving a 40 foot robot wouldn't be so bad; he imagined making love to one sure as hell wasn't.