The Doctor had decided to dye his hair.
"Well, Rose, not going to be regenerating anymore," he said cheerfully. "And that means I've got to find another way to be ginger."
"Yes, but…you're going to dye it?" she asked. "I like your hair, you know. It's nice. Suits you."
"But I want to be ginger!" he'd whined, and it wasn't like it was her hair to control, so she'd sighed and agreed to buy him some hair dye. Once he had the packet, he'd frowned, proclaimed it to be "not ginger enough," and proceeded to add some sort of strange alien chemical to it. Rose had her doubts about changing the composition of the stuff, but he'd insisted that it would be fine, and he was the Doctor, after all.
"Are you sure you know what you're doing?" she asked him, arms folded as he shooed her out of the bathroom.
"Yes, yes, go on, get!" he ordered, waving one arm towards the hallway and grasping the bowl containing the dye in the other.
"It's just that you've never done this before—" she tried to protest as he ushered her out, closing the door so that it was only open a crack. He peered at her with one eye, and she could tell from his voice that he was grinning.
"Rose Tyler, I am nine hundred and seven years old. Don't you think I know how to apply a bit of hair dye?"
"No," she said as the door slammed shut the rest of the way.
"I'm pretending I didn't hear that!" she heard through the door, and she couldn't help but laugh as she turned away and headed downstairs. This would take a while, and if he was going to refuse her help, she'd just have to watch some soaps while she waited.
After almost half an hour, she heard trainer-clad footsteps bounding down the stairs over the noise of the telly, and she pressed the mute button as she turned around.
"Are you ready?" he asked with a big grin as he charged into the room, a towel covering the top of his head. "It's been twenty-nine minutes and forty-two seconds. Just eighteen more seconds to go!"
She grinned. "Well, that's a bit precise, innit?"
"I can't risk anything going wrong!" the Doctor said, in a voice so serious he could almost be discussing a Dalek invasion. "This took forever, d'you realize? Don't want to have to do it all over again!"
Rose opted not to tell him about touchups. "How much longer now?"
"Three!" he said as though on cue. "Two! One!" And on one, he whipped the towel off his head in one fluid motion. Rose had been grinning in anticipation, but upon seeing the top of the Doctor's head, her jaw dropped open.
Tufts of very ginger hair had fallen off with the towel—lots of tufts, as a matter of fact. There was barely anything left on top of his head. He might as well have been completely bald.
"Well?" he asked, not seeming to notice. He twirled around in a circle, showing her the back of his still very bald head. "What do you think, Rose Tyler? Am I…ginger?"
"I…" She didn't have the heart to break it to him. "Doctor, I…"
"You're speechless!" he exulted. "That's brilliant!"
"No, I…Doctor, what was that alien chemical you used?" she asked, somehow managing to find words.
"Oh, nothing much," he said with a wave of his hand. "Just a simple Atraxi mixture. Not exactly designed for dyeing hair, mind, but it worked, didn't it!" His grin spread from ear to ear. Rose had almost gathered up the courage to tell him that it had not, in fact, worked, when he reached up to run a hand through the nonexistent hair and his face fell. "I—wait. What?"
And before she knew it, he was turning around, racing back to the bathroom, and it took her a moment to spring to her feet and run after him. When she got up there, he was staring at the mirror in horror, running both hands over his head. The remaining tufts had fallen out into the sink, and when he saw her come in, he whirled around and gave her a plaintive look.
"Rose, my hair's all gone."
"I know," she said. "I'm sorry."
"It's all gone," he repeated, sounding like he was in shock. "All of it. Gone. Just gone. How am I supposed to be ginger now?"
"Well, there's…there's always wigs?" she offered. "Not exactly the same as having actual hair, but—"
"Wigs!" he cried, his face lighting up. "Oh, Rose Tyler, you are brilliant!" He grabbed her arms, pulled her close and pressed his lips against hers, and for just the briefest of moments, she didn't notice the residual dye on his hands seeping into her nice denim jacket.
Then he was gone, racing back downstairs like some sort of hyperactive child, calling, "Come on, Rose! We've got to go to the wig store! They do have those, don't they?"