Harriet Jones: Did you notice when they fart, if you'll pardon the word, it doesn't just smell like a fart, if you'll pardon the word, it's something else. What is it? It's more like, um... Rose Tyler: Bad breath. Harriet Jones: That's it! The Doctor: Calcium decay. Now that Narrows it down!.. Calcium phosphate. Organic calcium. Living calcium. Creatures made out of living calcium. What else - what else? Hyphenated surnames. Yes! That narrows it down to one planet! Raxacoricofallapatorius! Mickey Smith: [sarcastically] Oh yeah, great! We can write 'em a letter.