At one point, Frasier asks to see Professor Tewksbury's "DSM". This stands for Diagnostic and Statistical Manual [of Mental Disorders].
In this episode we learn that Gil Chesterton's never seen (and thought by many in the show to be non-existent)wife Deb is a member of the National Guard.
In the Cheers episode, "I Kid You Not", it is revealed by Lilith that Frasier's mentor is actually named Bennet Ludlow who had a son with Carla, not Professor Tewksbury.
(Frasier has been pretending he is a caller on his own show)
Frasier: Sometimes it helps to write yourself a letter...
Tewksbury: He's already got himself on the phone.
Frasier: (frustrated) I don't know what he wants!
Tewksbury: Then why do you keep trying to bury him in psychiatric exercises?
Frasier: Because that's all I have!
(Tewksbury gives him a knowing, sad look)
Frasier: I'm sorry, caller, I can't help you.
Dr. Tewksbury: (On the phone) Yes, dear, I know we have reservations but one of my former students is having a minor crisis. I'll be there in half an hour.
Frasier: (shouting out the window) WHAT DOES IT ALL MEAN?
Tewksbury: Make it an hour.
TV audiences will likely best know Rene Auberjonois (Professor Tewksbury) as Odo on Star Trek: Deep Space Nine.
Title: Frasier's Edge
The title of this episodes is an allusion to Somerset Maughm's novel of self-exploration and search for meaning, The Razor's Edge.