In reality the kitten in the MTM logo is yawning. Since the cameraman couldn't get a usable shot of the cat actually meowing, the footage was used and a meow dubbed in.
A three-minute mini-pilot, titled "Love is All Around," was produced for CBS Network executives in an attempt to sell them on the casting of Edward Asner as Lou Grant.
When the famous opening credit sequence was reworked for Season 3-4, the Mary crew was being followed by a news team for the talk show program "Moore on Sunday". Both the news crew and the police officer escorting the Mary team were pressed into service for one of the clips (when the Mary Richards character has to duck to avoid being caught on film as the "news" cameraman swings his camera around in the direction the officer points).
Exteriors of Mary's residence show that the apartment with the balcony (which would be Mary's, based on the interior shots of her apartment) is on the top floor, yet Rhoda's apartment is upstairs from Mary's.
In the first season installment "Divorce Isn't Everything", Mary mentions that she can't speak French but can speak Spanish. Later in the series, while at a Mexican restaurant, she indicates that she can't read the menu because she took French in college.
On the newsroom wall there are various world clocks like you would see in a typical newsroom of that era. In the center is the Minneapolis/St. Paul clock, and to its left is a Chicago clock. Minneapolis and Chicago are both in the central time zone, so there is no need to have two different clocks. Furthermore it can be seen that the Chicago clock is set roughly an hour ahead.
Ted Baxter: I always like to think that our little newsroom was one big happy family. In my innocence, little did I suspect we'd be harboring a backstabber in our very bosom. I'm going to reveal the name of that person. The backstabber is...