"Why must I drink it!?" Potter argues with Malfoy

"Now potter. You will drink this because I brewed it, it's only fair anyways you'll only get a wolf tail and ears which you can hide, and the ability to transform anytime into a werewolf. Don't worry it's only temporary, it lasts a week." Malfoy states

"A week!?" Potter yells as he grabs the potion to drink it.