Off the cuff I might suggest a humor tonic...It jogs the funny bone. When an assistant drinks it and nothing happens the Doc hits his funny bone with a small hammer.
Is it true that a groan is as good as a laugh?

Maybe memory tonic... It doesn't work but the person doesn't remember why he took it in the first place.
P.S. How about printing up some "Tonic Labels" with your/his contact information on them?