"It is hard to figure out. Very, very hard. Not the sort of thing you teach yourself unless you're me." He frowned a bit, considering what little he knew of River from the Library. She had known his name; he had assumed, when Amy had brought up the subject of River's driving, that one of him must have taught her. If his future self--or rather, his other self's future self--hadn't taught her, did that mean a future future Doctor would teach her. It was all becoming incredibly confusing, so he decided to let the topic go.
"Leather bikini? That would have been Leela." He fell silent for a moment, somber, as he thought of the woman who had barged her way into his TARDIS and stayed with him until she had chosen to settle down on Gallifrey with a Time Lord for a husband and Romana as the source of her professional devotion as a bodyguard. "Rose would have looked like she belonged in your era, all pink and yellow. Well, maybe not so much pink, anymore. She seems to have taken to wearing blue. This blue, actually," he said, raising an arm to indicate the color of his suit.