For the most part, TJ was following along on what John was saying, right up until he said that if she wanted science, she'd have to get them to wake up McKay. She'd only ever heard of one McKay attached to the Air Force and the man wasn't a member of it. He was a Canadian, but he was a scientist and it struck her as odd that John would pick such a random name.

That confusion shows on her face and she turns to let Ianto fill her in on the royalty and nobility of the people below and then he confirms what had just gone through her head: McKay, to the two of them, is a Canadian scientist. A grumpy one.

"Wait. Do you mean Rodney McKay?" Because that man, as far as she knows, is nowhere near Earth and hasn't been for years, which mean John Sheppard isn't an Air Force Colonel stationed on Earth, either.