The character of Lurch the butler was originally not supposed to have any lines at all in the series. However, in the pilot, when the bell rang to summon him, Ted Cassidy ad-libbed the famous line, "You rang?". The line got a wave of laughter from the crew, and Lurch was given that line to say in almost every show (as well as the usual complement of grunts, growls and even some actual lines of dialog every so often).
The director of the pilot, Arthur Hiller, would go on to earn international acclaim, directing numerous feature films, including earning an Oscar nomination for Best Director (for Love Story (1970)). Prior to directing the Addams Family pilot he was a veteran director of television, this episode was one of the last TV projects he worked on.
Almost the entire set was pink. It photographed better in black and white.
Although a matte painting of The Addams Family House is used throughout the course of the show, a real house once located at 21 Chester Place (on the corner of W Adams Blvd) in Los Angeles, California was used in this episode for exterior footage and in the background during the show intro (Where Gomez is filing the gates). It was also used in publicity photos for the show with John Astin (Gomez) standing in front of the house in different spots and poses. However, the house didn't have the full third floor and tower that they had imagined. So instead of trying to buy it and fix to their liking or constructing an actual full-scale front or shell of the home on a studio lot, they opted to use the matte painting which could be altered for different moods/scenes. The house was also used exterior wise in Seven Days in May (1964).
"Like Mother, Like Daughter" --- Wednesday very deliberately and politely thanks Thing for the mail, just as Morticia always shows grateful appreciation whenever Thing assists her.