Bucky has a vine. 

Bucky has a vine that consists entirely of short videos of Steve doing totally mundane things -putting on his socks, wiping down a counter, hunched over a drawing pad- while he sings Boss Ass Bitch quietly in the background. 

Steve has absolutely no idea, either. He doesn’t realize Bucky is filming him, ever. He just assumes Bucky likes that insufferable song way too much, with how often he sings it.