A/N: This is part of a prompt challenge I'm doing on LiveJournal. This time, the prompt was "happiness".
It was a rare moment, and Sideswipe could only think that he was the only one allowed to really enjoy it for what it was.
Sunstreaker often smiled. Oh yes, that bitter little 'slag off' smile that he was so fond of. He flashed it at Red Alert when he was told to keep within the boundaries of the Ark, at Ratchet when told to not over exert himself after a round of Jet Judo, at Inferno, First Aid, Hound, even Prowl when he was feeling especially daring. (Never at Prime; no, Sunstreaker was boundary-pushing, but not stupid.)
Sunstreaker was reckless and ambitious and artistic and wouldn't take any kind of scrap from anyone in the Ark. Maybe that's why Sideswipe liked him so much when others didn't. Sunstreaker would back talk and challenge authority and get himself into trouble to help his twin. Escape from the holding cells during his punishment, and not care if anyone caught him.
Because of this kind of attitude, he came off as dangerous. The others steered clear, and Sunstreaker only proved them right with that smile. That 'slag off' smile that everyone had gotten so used to over the stellar cycles, the one that scared Autobot, Decepticon, and organic alike.
But it was these kinds of moments that made him realize why he really loved his twin. Sunstreaker demanding him to hold still – "I can't paint you with you wiggling like that" – and when Sideswipe refuses, he takes the brush and paints a stripe of red-orange along his faceplate.
Laughter. So rare, and it's coupled with a smile. Not that little 'slag off' smile, though Sideswipe would've loved that too. No, this was genuine, a smile that lit up his optics, and he shone bright and golden in the sunlight from the window, perfectly polished armor sleek and optics bright blue with something he hadn't seen in such a long time…
Happiness.
It was a rare moment. So Sideswipe learned to treasure it, because he knew that tomorrow it would be the bitter smile again, the one that frightened him slightly – not for his own safety, but the fear that Sunstreaker would get himself too deep in and be unable to get himself out – and he would no longer be a twin, a lover, a friend; he would be the sociopath that everyone feared.
Sideswipe held onto these moments, because he knew they were fleeting, and learned to be grateful for the happiness, however brief it may be.