The butter dish incident

 

"That lot won't come cheap," said George, with a quick look at his parents. "Lockhart's books are really expensive...."

"Well, we'll manage," said Mrs. Weasley, but she looked worried. "I expect we'll be able to pick up a lot of Ginny's things secondhand."

"Oh, are you starting at Hogwarts this year?" Harry asked Ginny.

She nodded, blushing to the roots of her flaming hair, and put her elbow in the butter dish. Fortunately no one saw this except Harry, because just then Ron's elder brother Percy walked in.

***

Harry Potter and the Chamber of Secrets, Chapter Four: At Flourish and Blotts