Other mistake: When the opening credits are shown, the door to the basement is in the kitchen. In the beginning of the series the door is still in the kitchen, but in later seasons the basement door is in the laundry room, but in the opening credits it is still in the kitchen.
Continuity mistake: During the show's first two seasons, we are told Roseanne had a more slender figure during her younger years and didn't start gaining weight until after she began having kids. Later in the Halloween episode, "The Ghost of Halloween Past," Roseanne is shown her past, and her younger versions are not slender.
Continuity mistake: Over the course of the entire show, the entrance into DJ's bedroom changes position. In the earlier seasons, the entry was on the right-hand side of the screen and the bathroom door was to the left. In later episodes, the characters entered the bedroom from the left-hand side. Everything else in the room remains the same.
Continuity mistake: In the episode where Jackie takes over the house, while Roseanne is at their parents. DJ comes in the kitchen and is sent in the laundry area for a shirt. Before he goes in there he is wearing a pair of dark jean with nothing on them. He comes back a second later with his head stuck in a shirt still with the same pants on. But when he finally pops his head through the shirt his pants have changed to a pair of stonewash, with what looks like bleach stains on the front. A wide shot of the kitchen in the next frame and his pants are back to the dark ones with nothing on them.