"So, where are we going today?" Martha asked the Doctor as she was finishing her breakfast.
"Oh, I know just the place. Earth, the evening of July 20, 2007," the Doctor replied, grinning at her.
"What's so special about that particular day?"
"Well, nothing's particularly special about that day, but the 21st is when Harry Potter and the Deathly Hallows is released."
Martha gaped at him for a moment before she managed to put a sentence together. "But… but you said that was too soon in my future; that I'd have to wait for my timeline to get there."
"Yeah, but you can be trusted not to spoil the ending for any of your friends, right? And," he added, becoming a bit more serious, "I think you deserve it after 1913."
Martha smiled at him for a few seconds, then hopped up and put her dish in the sink. "Come on, to the console room!" the Doctor continued.
"Hang on, I want to get dressed up for this. The wardrobe must have a Harry Potter shirt, or at least some house scarves."
"Well, you know where the wardrobe is. But be quick!" he added as Martha exited the room.
Fifteen minutes later she entered the console room, wearing a T-shirt with the Hogwarts crest on it and a blue and bronze striped scarf around her neck.
"Ravenclaw?" the Doctor asked, noticing her scarf.
"Yep. What about you, what house would you be in?" she asked.
"I've never been able to decide on one. I think it'd change from one regeneration to the next, anyway."
"Hmm. You're geeky enough for Ravenclaw, but you've got the reckless bravery for Gryffindor, too."
"Well, we'd need the sorting hat to know for sure."
"Oh!" exclaimed Martha, suddenly remembering, "I found these for you." She reached into her pocket and pulled out a pair of round glasses frames and a thick red pencil.
"Oh no, I am not dressing up for this."
"What, is it beneath your dignity as a not-pompous-at-all time lord?" Martha asked, grinning. "Come on, it'll be fun. Everyone else there will be dressed up, I'm sure."
"Alright, fine," the Doctor grumbled, taking the plastic frames from Martha and putting them on. "What's the red pencil for?" he asked, eying it suspiciously.
"You need a lightning bolt scar to complete the look. Come here, I'll draw it on your forehead."
"There's no way I can get out of this, is there?"
"Nope. Now stand still," Martha replied, standing on her tiptoes to reach the Doctor's head better. "Stop wrinkling your forehead."
After a few seconds she stepped back and admired her handiwork. "Perfect," she declared.
The Doctor examined his reflection on a shiny bit of TARDIS machinery. "I look silly," he complained.
"Maybe, but that's part of the fun, isn't it? And I'm sure there'll be plenty of other people there wearing silly costumes."
"If you say so. Now come on, we have a book to get!"
Several hours after they returned to the TARDIS, with a copy of Harry Potter and the Deathly Hallows in hand, the Doctor found Martha curled up in the library, sobbing over the book. She looked up at him long enough to say, "No judgment. You told me you cried too."