Revealing mistake: When Dan calls Becky, there is a shot of her and Mark in their Minneapolis apartment. This is the exact same set that is used later for Darlene's Chicago apartment when she goes to college. The fireplace shape and style, the wallpaper, position of the bathroom door, and the windows are exactly the same. The only difference is that the Darlene version looks shabbier.
Revealing mistake: After Charlotte picks out a dress with Roseanne in the kitchen, and she tells Darlene that she should also go to the prom, she runs from the kitchen like she is going home, but she is running between the kitchen and outside wall of laundry room. (00:08:00)