Harriet Jones: When they fart, if you'll pardon the word, it doesn't smell like a fart, pardon the word, it's like something else. What is it? It's more like um...
Rose: 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 surname! YES! That narrows it down to one planet: Raxacoricofallapatorius!
“Aliens of London”