Okay, your box is a spaceship. It’s really, really a spaceship. We are in space!
Before Clara walks into the TARDIS in totd, she pauses to reconnect the phone that is left hanging off the hook. At the time, it seemed like it didn’t mean much. With the new knowledge of series 8, I’m pretty sure that the phone was left hanging because the Doctor had just finished using it to call Clara’s phone. He knew he wouldn’t have much more time to talk to her as his eleventh self and he wanted to make sure she would adjust to Twelve. That phonecall is his last goodbye.