Disclaimer: I do not own Transformers, nor am I making any profit from this. I don't even own the plot bunny, which I got from livejournal. I have no idea who was the original owner of this plot bunny, and I've tried and failed to find them again, so if anyone knows who came up with this, please let me know. All I know about it is that it was the first plot bunny in that entry.

I'm sorry I turned this into a bit of a crack story, but I just couldn't resist!

Optimus first got hooked on it when he was banned from duty and confined to his quarters. To his surprise, he found it quite relaxing, giving him time to sort through all of his thoughts—something he rarely got the chance to do. After that, he started doing it whenever he got the chance, but always in secret. It was so simple, so addicting, a much needed break from the chaos of running an army.

He managed to keep it up for sixteen vorns before he was discovered.

Prowl sighed in annoyance—he'd been forced to take a detour due to one of the twin's pranks. Sideswipe had literally made a hole in one of the main corridors, and until it and the dozens of other holes could be fixed, he'd had to look over the blueprints for the Ark to find a new route to the rec. room. He found one.

He just wasn't expecting to find Prime, kneeling on the floor, scrubbing away, a bucket of cleaning solution next to him, and humming. He froze, logic processors scrambling to come up with a logical explanation.

"Prime?" he asked, struggling to keep his voice neutral.

Optimus froze, looking up with wide optics.

"What are you doing?"

It took Prime a while to answer, obviously looking for an excuse. "Cleaning. It's very relaxing," Optimus said finally.

Prowl, on the verge of crashing, was distracted by a cloth being thrust into his hands. He stared at it dumbly.

"Why don't you try it?"

After a moment, Prowl knelt down next to his commander, trying not to think about how illogical the situation was, and started wiping. A few breems later, he realized he'd actually relaxed. He glanced at Optimus, who had started humming again, and decided that maybe he had a logical reason after all.

After the hallway was clean, Optimus and Prowl parted ways, Optimus hurriedly retreating before Prowl could complain about his hobby, and Prowl retreating to find Energon-the reason he'd taken a detour in the first place. Prowl was halfway to the rec. room when his battle computer froze and he crashed, toppling over face first, logic processors unable to handle the fact that he'd found cleaning, of all things, relaxing, and that he'd been doing it with Optimus Prime, of all mechs.

Optimus Prime's secret remained a secret to the rest of the Ark, as it was never spoken of by Prowl, since every time he thought about it, he crashed.

Original Plot Bunny:

1. Optimus Prime has a guilty secret... He likes cleaning. It's actually quite relaxing. What would the reaction of, say, Prowl be if he came across him with a bucket and brush happily scrubbing the floor of a lesser used corridor in the Ark - and humming?

(Minor edits June 28, 2013)