The filly must have been only a little older than Applebloom and her friends, but the smile she wore was starkly out of place on her youthful features. It was much too knowing, much too smug, much too jaded and cold to belong on someone that young.
"You'd be surprised what you can find by looking up pony in a blue box" she said cooly "I understand more about you than you know....Doctor

When Twilight, beset by a cold, asks the Doctor to get her some soup, she didn't expect any crazy adventures. She certainly doesn't expect to be stranded in the wrong time, chasing after a loose-cannon filly with the potential to irrevocably change time, and absolutely no qualms about breaking the rules.
In retrospect, the soup probably wasn't worth the trouble.

Cover picture by The Pony Librarian