John Rubinstein, who plays the slimy gallery owner, was also a skilled composer, having done scores for numerous films and television shows including "Jeremiah Johnson", and "The Candidate"; "Family" and "China Beach". He is the son of concert pianist Arthur Rubinstein.
When Roz (Peri Gilpin) says to the waiter "and spill a little into the glass." She says the same line in an early episode of Wings where Ms. Gilpin played a brassy character who ordered the bartender to "spill a little into the glass".
Martha Paxton actress Rachel Rosenthal had a small handful of screen credits, but she was mostly known as interdisciplinary artist - a painter, among other things.
Martin (John Mahoney) dismisses Frasier's (Kelsey Grammer) call to the police as frivolous, however, in reality, forgery is a serious crime. The gallery would have been subject to criminal charges if they had knowingly sold a forgery, and Frasier could have easily won any court action against them.