[When she starts, he is--for just a moment--afraid she's somehow figured it out and, not only that, is about to actually say it. So for that moment he's frozen, a brief look of shock crossing his face, but it's under control an instant later as he hears the rest of what she's saying and realizes it's just a stupid joke. An actually funny, cute stupid joke.

So he manages a genuine smile, even if it might be slightly shakier than usual, voice light when he responds.]

My coworkers deserved having to put up with Fitz, and besides, it wasn't his fault he had to end up at the FBI. But that last part doesn't even count as psychoanalyzing; anyone could tell that much.