When they show the outside of the car dealership at the beginning, you can see a few palm trees behind the building. Rather out of place for Minneapolis.
The "brand new" green Mustang convertible that Mary ogles in the dealer showroom while her own car is being repaired has a dent in the rear quarter panel.
"Put on a Happy Face" is the only episode of the series that did not end with the traditional "meow" of the orange MTM tabby Mimsey. Instead, Moore herself appeared in the circular MTM logo doing her best Porky Pig impersonation: "Th-Th-Th-That's all folks!"
Lou mentions his three daughters names: Sara, Ruthie, and Janey, and his four grand kids names: Amy, Abby, Eric, and Matthew.
This is the first glimpse of, or even reference to, a lunchroom at the office. It has four vending machines and at least three tables.
Lou mentions his first job was writing "Thoughts in Rhyme" under the pen name of Lois Hammersmith for the Detroit Free Press.
Continuity Error: When talking to Rhoda, Mary tells her that she introduced Ted and Georgette. But in the season 3 episode "Rhoda Morgenstern: Minneapolis to New York," Ted and Georgette meet at a going-away party for Rhoda at Mary's apartment by introduced themselves. Georgette was a co-worker of Rhoda's at Hempill's Department Store at the time.
In this episode, Georgette says her height is 5'6".
This is the first time you see the hallway and staircase outside Mary's apartment.
This episode marks the first appearance of Georgia Engel as Georgette
According to this episode, Rhoda decides to move to New York, but doesn't. But this issue is never discussed again until the season 4 episode "Best of Enemies", where she actually moves out.
Another rare episode with a scene continuing during the closing credits (with no music). Lou told Ted to stay in his office until he comes in, then decides to cool off and wait until morning before chewing out Ted (forgetting Ted is waiting in his office), and leaves. The closing credits roll over a dark newsroom, with Ted peeking out of Lou's office, and whistling.
Rayette the Waitress either quit working in the cafe or has 2 jobs, as she's a waitress in the restaurant Lou, Mary and her dad go to, which appears to be the same one Randy worked in on the 2nd season episode "Feeb", although the booth they sat in has different color leather now.
Beth Howland who played Linda Foster, is best known for her portrayal of Vera the dingy waitress from Alice.
Ted's tomato slicer commercial must not have went too well...he has bandages on several fingers.
Lou mentions Ted makes $31000 a year, plus he ends up getting a $25 a week raise.
Normally Mary has a small portable black and white TV, but on this episode, she has the same Sony Trinitron color TV that's always shown in the newsroom next to Murray's desk.
Jerry Van Dyke had previously appeared with Mary Tyler Moore on a few episodes of The Dick Van Dyke Show.
Goof: When Wes walks into Mary's kitchen after finding out he didn't get the news anchor job, the film freezes after the door closes long enough for him to say something and then it unfreezes and he walks back out from the kitchen.
Mary's rent is now $135 a month. In the 2nd season episode "More Than Neighbors", it was $125 a month.