Jack shot a glance over his shoulder, wondering what Ianto thought of all of this. Hell, Jack was sitting in a state of shock though managing to keep his mouth from falling open. The expression on Rose's face matched his own feelings even if Jack was better able to hide things.
He would like to be able to move past this phase of being completely shocked and move into more important things. Namely the idea that this was going to create one hell of a paradox -- one that Jack wasn't sure if they should all be talking. He was expecting something to either fall from the sky or spring forth from within the earth.
"So we have the Doctor and the Doctor," Jack said, interrupting Nine's diatribe. "One of which who will babble on until time itself runs out." He paused. "Actually -- I don't know which one would talk for longer. And, too, nothing's swallowed us whole with the paradox we have going.
"So how the hell is this working?" Jack rubbed his chin thoughtfully. "Or, could it be that physically they're just different enough to avoid being the same person." Jack grinned suddenly. "Has to be the ears. That's what did it."