I had no idea until I watched it today! It was everything you would hope it to be. :P

Walter: ….I'll have 50 milligrams, please.
Dr. West: Well, that… that's quite a high dosage.
Walter: I have quite a high tolerance.

The choice of John Noble as Sherlock's father? Perfection. I can't wait to see more razor-sharp banter from these two.