"Sunglasses," said Jack blankly, staring at the Doctor, who nodded proudly. "Sonic. Bloody. Sunglasses."

"Yep," said the Doctor cheerfully, slipping them on. "Don't you like them?"

"Yeah," Jack said, frowning and folding his arms. "Yeah, I guess, but-"

"But what? Do you have an issue with my lovely sonic sunglasses?" When Jack took more than a second to respond, the Doctor ploughed on. "I knew it! You're nothing but a philistine, Jack Harkness- a philistine!"

"It's not that," said Jack hurriedly. "But seriously- who looks at a pair of sunglasses and thinks, 'ooh, these could be a little more sonic'?"