"'Potter! What are you doing?'
'Clearing up my armadillo bile, Professor,' said Harry innocently ..." (GF27)
Armadillos are small armored mammals found throughout the Americas; the species is most diverse, however, in South America.
The bile of the armadillo is used for making potions, including Wit-Sharpening Potion. Harry spilled his armadillo bile on purpose during a Potions lesson in order to listen to a conversation between Snape and Karkaroff (GF27).
In CS/f, Hannah Abbott can be seen with an armadillo in front of her during the Fera Verto spell practice in the first transfiguration lesson of the term prior to McGonagall's explanation of the Chamber of Secrets.
This reference to the armadillo being part of the Wit-Sharpening Potion may be in homage to a particularly funny advertisement which ran on British television. In the advert, a devastatingly dim country fellow is offered a Dime candy bar, which is "smooth on the outside, crunchy on the inside." He says that he prefers to eat armadillos, which are "smooth on the inside, crunchy on the outside!" The presenter says "You're a bit thick, aren't you?" and the country bumpkin nods happily. Thanks to Wayne Childs for noting this connection.