"It's beautiful!"
Donna Noble gasped as she and the Doctor stepped out onto the surface of yet another alien world. The Doctor, who had seen more unfamiliar planets than Donna could even count, seemed similarly awestruck by the fantastic sight before them.
The sky was a light shade of lavender, with puffy white clouds skimming across it. Donna looked upwards, marvelling at the unlikely hue.
"D'ya think they ever wish it was blue?" she muses with a chuckle. The Doctor shakes his head, smiling.
"Hard to say. Why, did you use to wish the sky was purple, back home?"
Donna shrugs. "Nah. Just sayin'. Cos you know people are never happy with what they've got."
The Doctor was surprised to hear such a thing coming from Donna Noble's mouth, but then again, a lot of things had changed about her since she'd been travelling with him. However, she was back to her normal self in a flash.
"Oi," she said, in a manner far quieter and subdued than he'd ever heard from her before, but still distinctly Donna. "Those things, over there...they aren't unicorns, are they?"
He followed her gaze, squinting slightly. Donna giggled and elbowed him.
"Maybe you ought to put on those clever specs of yours. Nothing wrong with needing glasses, right, spaceman? At least, that's what Mum always told me, but only because I used to make fun of Alice Sheppard back in school, and..."
The Doctor placed a finger over her lips. "Hush, Donna." Her eyes twinkled merrily, but she hushed, at least for a moment.
"Are they unicorns?" she asked again. The Doctor screwed his face up into the expression he got when he was trying to think of how to explain something and explain it at the same time.
"Yes. Technically. Well, no. Not really. I mean, the word unicorn is a corruption of unihorn, meaning one horn, and they've definitely just got one. Well, usually. Sometimes it breaks off. And they haven't really got magical powers. Well, probably not, anyway. And they can't fly. But for all intents and purposes, I suppose you might as well call them unicorns."
Donna laughed. "Alien unicorns. Living on a planet with a purple sky. What a laugh!"
The Doctor ran a hand through his hair. "S'pose it is, yeah." He looked at her. "You've got unicorns on Earth, you know."
Donna fixed him with an "oh, please" glare. "I will believe that you're a million and a half years old, and that aliens really do want to invade Earth, and that there is life on other planets all over the place, and I will even believe in 'alien unicorns,' but there is no way that they live on Earth." The Doctor grinned and continued.
"You do! Because what's a unicorn but a creature with one horn, after all. You've got them, they're just fat and grey and live in the desert. They're called rhinoceri."
Donna elbowed him again, harder this time.
"Ow!" he protested. Donna gave him a pointed stare.
"You're impossible, spaceman."
He grinned. "No, just highly improbable." He held out his arm, and Donna took it with an exasperated sigh. "And I'm only nine hundred and five."
