Early on, Leonard Snart's smirk was infuriating. Smug bastard. He had the world on a string and he knew it. Several times, she would have loved to slap that smirk off his face.
As their time on the ship progressed, the smirk became more annoying than anything else. Yeah, he was still a smug bastard, but more often than not, he had the comeback or the moves to back it up. She almost respected that.
After their time freezing in the engine room, she began to see what the smirk really was: survival. It was a defense mechanism for all those years as a vulnerable, abused son. There were years and years of pain buried in him, but the world would only see his self-assured outside. It might have been a front, but damn it, he'd never let anyone else see that helpless side again. Just this cocky jerk. It was safer that way.
Until Sara started to see through that exterior. There were many more layers to Leonard Snart (and not just his wardrobe). Captain Cold kept the world out, but sometimes Leonard would let Sara in. And from there, it was history.
After surviving the frigid engine room, enduring other adventures, the debacle at the Vanishing Point, and his miracle rescue after an apparent death, Sara saw a much different side to Leonard, though she was definitely the only one.
The smirk took on a different meaning with and only with Sara. A glance across the breakfast table… approval when she gave a particularly snarky response to Rip or Raymond… a look of admiration as she fought like a warrior… she could feel his mouth lift into a smirk as he looked at her from under the covers, pleased with himself and the noises she was making… satisfaction when he actually managed to legitimately pin her in a sparring match (and not wondering if she let him win that one)… staring up at her as she straddled him, amazed that she was actually with him. Those smirks had become a love language now and only Sara was fluent in it.
His smiles, all the more rare, were just as precious. The smirks were no longer annoying (well, most of the time), but were actually loving. But the smiles were joyful. Holding her after love making (even early on when that term still made him a little twitchy)… pride when he did something she appreciated… warmth when she accepted his proposal or when they exchanged vows… complete awe when he first held his daughter.
But the smirks, for as much as they once made her blood boil, now they made her heart skip a beat. She could see him across a crowded room or across the holo-table and that damn smirk would make her weak in the knees. She always hated weakness, but for him, she'd make the exception. This was the love that made you weak and strong.
And don't even get her started on that man's eyes…