She doesn’t know she does it, and he has never told her, not even after sixteen years. When they were first at school, they’d be Muggle tunes, most often Christmas carols—even in springtime. When she was anxiously preparing for her OWLs, they had been mostly upbeat and encouraging, except for one Weird Sisters tune he was certain she had never realized she knew well enough to duplicate it while studying. During the dark days of uncertainty and grim preparation for the war, she would quite maddeningly get herself stuck on the most inappropriate Celestina Warbeck songs…
He realizes that this is part of why he fell in love with her—the unconscious optimism that is such an integral part of her character. She had never given up, not even when the sky seemed to be falling and loved ones without whom the world would never be the same had been ripped from them without warning. They had clung to each other, felt guilty together as they took the time to fall in love while the rest of their friends fought the war that seemingly would not end. It had, of course, ended, and he knew they had been incredibly lucky to have survived it.
He hadn’t let her know that one of the reasons he’d pushed for the wedding so soon after their victory was that he couldn’t bear the thought of her studying without himself as a captive audience. He’d had more important reasons, of course, but something in him knew that if he let her know about the things she did unconsciously, she’d stop, even if he protested that he loved them. Each endearing little quirk of hers, therefore, became in his mind a testament to his love for her.
The most powerful memories he had of her little habit had been while she was pregnant with their daughter, the ancient potions and transfiguration manuscripts replaced by Muggle how-to books, and the outrageous love songs of Celestina succeeded by the great masters, as though their unborn child could tell the difference. He had, though, and the fact that she’d started humming music that was considered of great cultural significance to their child before it was even born was to him, a testament of her love for him.
He stops himself in the middle of his reverie, remembering that he has a surprise for her tonight. He doesn’t know—had never thought to ask—what exact day she’d gotten her Hogwarts letter, but he knows when the first day of school had been, all those years ago. Getting to his feet slowly, so as not to disturb his wife as she works, he walks unhurriedly into the kitchen to retrieve the cake. As much as he would have loved to have baked it himself, he had decided to settle on a confection from her favorite bakery, something she only gets to eat on Lily’s birthday, which is as far from September as possible.
Inevitably, his hands fumble with his wand as he juggles the elaborate cake and two plates, making enough noise to cause his wife to come to investigate.
“What in Merlin’s—” she begins to say, but he interrupts her, too excited about his plans to allow himself to keep it a secret any longer.
“Happy Sweet Sixteen!” He nearly hands her the cake before realizing that this would be a foolish thing to do to a flabbergasted woman, who might very well drop it.
“Happy…what?” she asks, rewarding him with the look she used when she thought he was daft.
“Sixteen years ago,” he says proudly, leading her to the most comfortable chair in the kitchen and beginning to cut her a piece of her cake, “you became a witch.”
The change in her is immediate, from complete incredulity to melting sentimentality. She stands up, moving around the table swiftly to clasp him strongly to her, their hands becoming slightly sticky from the icing as their fingers intertwine. This kiss was well worth keeping the secret of her magical birthday until tonight, he thinks to himself as his hand tangles in her hair and they each forget about the cake entirely.
Hours later, when they’d finally shared a piece of cake, done the cleaning up, and gone to bed, he lay beside her with a smile on his face, remembering all the reasons he’d fallen for her in the first place. Before finally drifting off to sleep, Harry thanks Merlin for the day when he’d finally realized he wanted to always be the melody that Hermione sang to herself when she studied.