Continuity mistake: It is known that Dorothy married Stan because she was pregnant and they were married for 38 years. However Michael is not 38 - his age is stated as either 23 or 30 in different episodes, a mistake in itself - and in the 2 episodes her daughter is in, she doesn't look to be anywhere near 38 either.
Character mistake: The number of years that Sal has been dead and the number of years that he and Sophia were married, constantly changes. In Season 3 Episode 5, Sophia says that she and Sal were married for 52 years. In other episodes, she says he's been dead anywhere from 22-30 years. If that's the case, given that Sophia is 80 at the start of the show, Sal would have died when she was about 50. Meaning that they would have had to be married since birth to be married over 50 years.
Continuity mistake: In one episode, Rose talks about being valedictorian of her high school class in St. Olaf. In another episode, Rose goes to night school (where Dorothy is her teacher) in order to get her GED because she never graduated from high school. While talking to rose about the class Dorothy states the class is for people who didn't get a diploma. Additionally, in the episode "Whose face is this, anyway" Rose mentions that she was in a sorority called the "Alpha Yams"; when the girls look at her strangely, Rose states "It was an agricultural college." She could not have gone to college without a high school diploma.
Continuity mistake: In series 3 Dorothy's son Michael, who is engaged to a woman 21 years older than he, is supposed to be 23. In Series 2, when Michael sleeps with Rose's daughter, Dorothy mentions that he is 29 years old.
Continuity mistake: Angela says that she and Sophia are the only ones left living in the family, but in later episodes their brother Angelo shows up.
Continuity mistake: Throughout the show, Rose implies through numerous stories that everyone in St. Olaf, explicitly including close family members, is just as dumb and weird as Rose herself. However, most of Rose's relatives we meet are perfectly normal people, including her adoptive mother, both of her daughters that we get to see, her biological father and her blind sister. During a dream sequence, her adoptive father appears and he doesn't seem to be unintelligent either, giving her good advice. Only her cousin Sven fits her description by being arguably even dumber than her.
Continuity mistake: In the episode when Dorothy is trying out for Jeopardy, she is sitting on the couch studying, When Sophia sits down to talk to her Dorothy is looking at a page with just words, It cuts to Sophia and then to Dorothy and the page now has pictures on it. You can still see the corner of the book when the frame is on Sophia and you can see that Dorothy did not turn the page.
Other mistake: Dorothy gets pregnant in high school with Michael. Dorothy plays a woman in her 50s. He was in his Early 20s when the show started. She wouldn't have been in high school age 30.
Continuity mistake: Whether Gladys Goldfine is alive or dead changes from episode to episode. For example in one episode, Sophia is mad at her because she doesn't take her out to a Tony Bennett concert and we see her apologizing to Sophia in the end, but in an earlier episode Salvatore's spirit told Sophia that Gladys has an affair with Charlemagne in heaven.
Continuity mistake: In the episode where Sophia loses her glasses, Dorothy answers the door and Sophia says "is this 6151 Richmond St?" In the episode where Dorothy has taken up smoking again and sets off the smoke alarm, Blanche and Rose rush into the kitchen, Blanche dials 9-1-1 and says "send a firetruck to 5161 Richmond, I'm on fire."
Continuity mistake: Blanche's attitude towards birthday parties changes throughout the show. Originally, she disliked them, but Rose changed her mind when she invited several men Blanche desired, as is seen in a flashback. In the same episode, the Golden Girls threw a surprise party for her which she was happy about. In a later episode, she hates birthday parties again (with Rose being baffled she doesn't like them), but is happy again at the end of the episode when Rose invites men to her party.
Revealing mistake: Throughout the entire series every time someone is cooking on the stove there's never any steam coming from the cookware. Also looking at the burners, it's an electric oven yet the burners are never orange indicating they never really "cook" food at all.
Continuity mistake: In the pilot, Blanche's bedroom is to the back left, not down the hall. From the series' second episode on, the lanai was out of the back left door and all the bedrooms are down the hallway.
The Engagement (a.k.a) Pilot - S1-E1
Other mistake: When Dorothy explains to Rose about her ex husband Stan she mentions he is a 65-year-old man. If they were in high school together and she's in her 50s wouldn't that mean he would be 50s as well?
The Engagement (a.k.a) Pilot - S1-E1
Other mistake: When Dorothy and Rose go back to Blanche's bedroom to ask her about her engagement to her BF Harry, they use the entrance that is normally used for the lanai. Possible set change.
Guess Who's Coming to the Wedding? - S1-E2
Visible crew/equipment: When Dorothy and Stanley are talking outside, the camera rolls into frame on the left-hand side. (00:22:48)
Revealing mistake: Dorothy is putting wet washcloths on Blanche's forehead. But if you look in the bowl on the table, there is no water in it at all. And when Dorothy wrings out the washcloth, only a tiny bit of water comes out. (03:05:00)
Continuity mistake: In this episode, Blanche was talking about how she learned of her late husband, George's, death. She said she got the phone call late at night and the officer on the phone (chewing potato chips), told her that her husband was killed instantly in a accident. But in another episode, Sophia made a comment about how Blanche was getting a pedicure while her husband was dying in the hospital. Blanche admitted to this, so it was not one of Sophia's smart remarks.
Visible crew/equipment: Blanche and Rose are rehearsing their tap dancing routine. At the end of the routine, Sofia walks in and the boom mic becomes visible on the top right of the screen, moving toward her. (00:32:15)
Continuity mistake: Blanche says she can't go to the Sinatra concert because her final exam is that night. In the first classroom scene, the chalkboard says that the final exam is in four weeks. But before Blanche gets home and tells the girls that her teacher wants her to sleep with him, Dorothy says the concert is in two weeks. It is the same day, since Blanche is wearing the same outfit and she wouldn't wait two weeks to tell the girls about her teacher.
Answer: Ice makers were a new invention, advertisement purposes.