Ew, you'll have to drink a potion of Goyle or Crabbe! Trying to repress that thought for now, you come up with a plan. It's simple really, what motivates those two the most? As far as you know, food. You ask Hermione to jinx a couple of muffins so that anyone who would eat them would fall asleep for an hour or so.
You wait for Crabbe and Goyle to leave the Great Hall and Wingardium Leviosa the muffins so they're situated in front of them. You have two particular fears about this part of the plan; first, what if they're not hungry, they are leaving the Great Hall after all, and secondly, who's thick enough to go ahead and eat something that mysteriously appeared to be floating in front of you?
But you needn't worry, upon noticing the muffins, both boys share an ecstatic glance as if they just won a lottery and sink their teeth into them.
It was smooth sailing from there - you get the hair, move them to the nearby closet and run back.
You can feel guilty later, now it's time to act!
Your reading prompt!
Hair-thin! Read a book that's no longer than 125 pages!