Revealing mistake: Shortly after the fight with Becky, Roseanne asks Jackie to go across the street to get her something to drink, so she can smoke in secret. After Roseanne lights the cigarette and walks near the register, Jackie's plaid coat can be seen in the door's window as she waits for the next scene.
Continuity mistake: When Roseanne & Jackie talk about Arnie, they act like they haven't known him long. Jackie even states, "I don't know him." Yet, in episode "Why Jackie Becomes a Trucker," Jackie sleeps with Arnie. Roseanne says all the girls made a pact in high school that none of them would ever sleep with him.
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.
Suggested correction: I had noticed the same thing and thought it was a continuity mistake. However, in Season 3, Dan mentioned building the back service porch where Roseanne does the laundry. There are two basement accesses, the one in the kitchen, and what was probably the outside entrance in the backyard that is now enclosed inside the service porch. The family prefers using that one. Most houses, mine own included, have multiple basement access, one inside the house and one outside. In my state, it's a building code requirement.
Visible crew/equipment: When the Conners' friends come over and say "Hey Jailbird!" to Dan, a microphone can be seen coming down and going back up in the top left corner.
Halloween - The Final Chapter - S8-E5
Continuity mistake: Roseanne becomes pregnant at the beginning of Season 7, and it is before the Halloween and Thanksgiving episodes, so she is in her first trimester during the holidays. However, Roseanne does not give birth until the following year in the Season 8 Halloween episode. Her pregnancy has lasted for well over a year.
The Last Thursday in November - S8-E8
Other mistake: Roseanne gave birth to Jerry on October 31st. That Thanksgiving, on November 21st, Jerry was only 3 weeks old. However, he is side by side with Andy sitting in a high chair on his own, sitting straight up, holding his own head up.
Into That Good Night: Part 2 - S9-E24
Visible crew/equipment: When Bev hears "movement" on the baby monitor everyone rushes toward Roseanne on the stairs, and just as Roseanne comments that they're all "scary enough individually," we can see the second camera appear at the left side of the screen. Then, when Bev walks through the bedroom's doorway, there's movement of the boom mic at the top left corner of the screen, and when DJ turns on the camcorder the end of the set is visible from the POV of the camcorder.
Continuity mistake: Roseanne brings in a plate of sandwiches after Dan brings home the new couch. She places the plate on the the small stand in front of her. Between shots, the plate switches to the stand in front of Dan and then back to in front of Roseanne.
Home for the Holidays - S9-E12
Revealing mistake: When the family is eating the Christmas cookies, look at the top of the screen. In the kitchen, you can blatantly see where the top of the kitchen actually ends, revealing gray panels. The Conner's ceiling never went up this high, so it is definitely set material.
Continuity mistake: Roseanne comes home and the kitchen cabinets are not painted/plain wood. In the very next shot from a different angle, the cabinet doors are painted.
Lovers Lanes - S1-E6
Continuity mistake: Dan tells Crystal that his shoe size is 11. A few months later during episode 16, "Mall Story", Dan tells a shoe salesman he takes a size 13.
Suggested correction: Some people wear different sizes depending on the type of shoe. Not necessarily a mistake.
Scenes from a Barbecue - S3-E24
Plot hole: All the kids and Arnie are about to play a basketball game. Darlene and Chuck Jr. battle in Rock, Paper, Scissors to see who picks first. They both throw scissors, and then Chuck Jr. says he gets to pick first. They should have done it over, since that would be considered 'a tie', he really didn't win. (00:12:10)
Continuity mistake: When a depressed Roseanne emerges from her bedroom after Dan has left her, she tells Nancy and Leon that she wants to turn over her and Jackie's shares of the restaurant to them. She says she wants Nancy and Leon to experience the same sense of accomplishment that she and Jackie felt when they first opened the business. However, Roseanne seems to have forgotten that it was Nancy, along with her, Jackie, and Bev, who started the restaurant.
Continuity mistake: In one episode, there is a bowl of fruit on the table in the living room. The boys start wrestling and they knock it down. In the next shot it's back on the table again, untouched.
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: In episodes when Darlene has just moved into her apartment, the bathtub is on the wall in front of the bathroom door. In later episodes, the tub is on the wall to the left of the door.
Continuity mistake: In "Guilty By Suspicion," Jackie hangs up her coat in her living room closet. This is the same door that, when she first moved into the house, led to the basement.
No Talking - S2-E12
Factual error: When Becky locks Roseanne out of her bedroom, Roseanne heads to the garage for a screwdriver to take the door off the hinges - an impossibility since the hinges are on Becky's side of the door. In the next scene, the door is off the hinges.
Suggested correction: Roseanne could have waited until Becky opened the door at a later time. She would have to come out at some point. Dan could also have ordered her to open it, and Roseanne then took it off the hinges. It was also Darlene's room, so Becky would have to let her in. Roseanne was making a point and to make sure Becky didn't do it again.
This is the most ridiculously convoluted "correction" ever. It was a monumental mistake, or at the very least, they hoped viewers wouldn't notice.
Yeah, not an impossibility whatsoever considering even if the door had to be forced open, it was going to be taken off the hinges. Classic 80's/90's parenting.
The Birds and the Frozen Bees - S7-E23
Continuity mistake: Roseanne and Darlene are sitting on the sofa discussing Darlene getting back together with David. The cuff on the sleeve of Darlene's sweater is partially turned down, and in the next shot it's neatly turned up.
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.