Philosophers in the Orchard

Derpy may not look the type, but she has a lot to think about. It's only after ponies go out of their way to talk to her about what's on her mind does she finally open up

When Applejack spots Derpy staring off into space, she wants to know if the lonely mare is all right. It turns out that Derpy has a lot to think about, including quite a few other pegasi who venture to Sweet Apple Acres in the middle of the night to do the same.