Remus Lupin: Neville, what frightens you most of all?

Neville Longbottom: Professor Snape.

Remus Lupin: Professor Snape. Yes, frightens all. I believe you live with your grandmother.

Neville Longbottom: I don’t want it to turn into her, either.

Remus Lupin: No… it won’t. I want you to picture her clothes. Only her clothes, very clearly, in your mind.

Neville Longbottom: She carries a red handbag…

Remus Lupin: We don’t need to hear. As long as you see it, we’ll see it. Now, when I open that wardrobe… here’s what I want you to do. Excuse me. (whispers to Neville only): Imagine Professor Snape in your grandmother’s clothes. Can you do that? Yes. Wand at the ready. One, two, three. (opens the wardrobe) Think, Neville, think.

Neville Longbottom: Riddikulus!

Remus Lupin: Wonderful, Neville, wonderful! Incredible!

From Harry Potter and the Prisoner of Azkaban (2004)