This is the first episode that Ted Knight does not appear in. He would also not be in Toulouse-Lautrec Is One of My Favorite Artists (1970) and Enter Rhoda's Parents (1972).
Interestingly, the two ex-NFL characters applying for the WJM sportscaster's job, John Schuck (as Frank Carelli) and Timothy Brown (as Timothy Brown), both appeared together in the movie MASH (1970).
In "Keep Your Guard Up," (S1, E5) Mary gives her address as "119 North Weatherly." In fact, the house which is shown in the establishing shots is at 2104 Kenwood Pkwy, Minneapolis, MN.