Wondering if they’d get the joke right now

Perusing Dr. Black’s blog – there was this comment:

9:06 AM I have two doctoral students taking their orals next Monday. Want them to know of my prayers. By the way, I’m thinking of doing the orals in German.

Followed by:

(*Joke*.)

Well, I chuckled, but I did wonder if they would be IF the good Dr. started the session in, well, German. So much pressure . . .