So, Author's Note time.

In response to questions put in reviews:

1. Q: Why are they the only ones to respond to the scream?

A:I have this stupid headcannon where Molly is a light sleeper, and she's gotten so used to Sherlock waking her up. The other students assumed it was a dream if they woke up, or are heavier sleepers (with the workload at Hogwarts, you'd be a heavy sleeper too)

2. Q: They transfigured Carl into a leaf?

A: Yes. Jim wants a trophy, and because keeping Carl's Want would be to conspicuous, he decided to keep the body, but as a nondescript leaf.