"When's your birthday?"
The Doctor frowned, sure he had heard wrong. "What?"
"Well, I was jus' wondering, 'cos you were keepin' track for me, an' I thought…" Rose trailed off uncertainly. "Never mind."
The Doctor stared uncomprehendingly at his pink-and-yellow girl for a moment. She flushed, embarrassed, and stared at her feet. "I'll jus'— " she jerked her hand towards the corridor and fled.
Nice goin' there, Skinny, a distinctly northern voice said sarcastically in the back of his mind. "Oh, shut up," the Time Lord grumbled at his past self. He made his way down the hall. "Rose?"
The TARDIS flashed the lights and the door to Rose's bedroom appeared, slightly unlatched. The Doctor took that as a sign he could enter. "Rose," he said tentatively, pushing open the blue door.
"'M sorry," the blonde hurried to say. "S'not my business. Didn't mean t' pry." She worried her lower lip with her teeth.
The Doctor sat down next to her on the bed. "I was just surprised at the question, that's all," he told her easily. "I'm over 900 years old. No one's ever asked about my birthday. I don't even know if I remember it."
The Doctor nodded solemnly. "Gallifreyan time measurements were different from yours, anyway. And birthdays weren't as important to Time Lords as they are to you humans. The Time Lords were a stuffy old lot. Only purpose birthdays had was purely factual, to keep track of age. They didn't celebrate—all that emotional stuff was viewed as being below us. Why're you so keen to know, anyway?"
"Well," Rose started, shifting nervously. "I thought, maybe, tha' I could do somethin' for you. 'Cos I can't really repay you for all the trips, an' I figured maybe I could get you a gift. If you wanted," she hurriedly added.
"Oh, Rose," the Doctor said softly, almost tenderly. "You do more for me than you could ever know. Just by being here. You want to do something for me?"
"It'd make me feel better," Rose said with a nod.
"Mm. How long are you gonna stay with me?"
"Forever," she answered, confused by the non sequitur.
"Forever, Rose Tyler, from you," the Doctor began, caressing each word in a way that made Rose shiver. "That's the best birthday present I could ever receive."