I introduce the temp to everyone at work by saying, "She'll be taking care of things while I'm away next month."
The people who know why I'll be out all make the same face - head tilted, lips pursed in a slight pout, eyes widened (and not that I doubt their sincerity, it's just a very specific face).
The temp, who doesn't know what's going on, is classy enough not to ask, but after enough people make the face, I explain to her about my upcoming surgery.
"And now you're making the face!" I say, making us both laugh.