This is the third of six credited appearances Robyn Millan makes in the series, each time playing Roz, a schoolmate for Patty and Cathy.
This is the third of four credited appearances Natalie Masters makes in the series, repeating her role as Mrs. Marlow, which she played one other time earlier in season 3: A Foggy Day in Brooklyn Heights (1965).
The painting Louie has hanging in his malt shop is a copy of Emanuel Leutze's "Washington Crossing the Delaware," painted in 1851 and depicting Washington and his Continental Army crossing the Delaware River from Pennsylvania to New Jersey on Christmas night 1776 to conduct a surprise attack against Hessian forces in Trenton, NJ.
In the first two seasons, the malt shop where Patty and her friends hang out is known as the Shake Shop and set up almost the opposite of the layout for the malt shop seen here, which is called Louie's Ice Cream Parlor.
This is the first of three credited appearances Ronnie Schell makes in the series, each time playing a different character. His other appearances occur in Patty, the Candy Striper (1965) and Fiancee for a Day (1966). At the time of his appearances in this series, he was already playing a recurring role as Duke Slater in Gomer Pyle: USMC (1964).