"How well do we really know him, though," Jack said, pushing a lock of Rose's hair behind her ear. "You may not be the same Rose I know, either." He tilted his head, studying her closely. "You look like her, you sound like her... so that's enough for me. Maybe it's the same way with the doctor, just the other way around. He may not look like him, or sound like him, but it's still The Doctor."