Plot hole: Before her date, Becky asks Roseanne to help style her hair. After the family teases her, Becky says she'll just do it herself. Shortly after, she comes downstairs with a perfectly executed and complicated French-braid hairstyle that would be all but impossible to have done by herself and in such a short amount of time.
Continuity mistake: Darlene and Becky's second-story bedroom window is on the side of the house and at the house's backside (D.J.'s room is at the front and the windows are also on the side). However, when the girls argue and throw each other's items out the window, everything falls into the front yard, as viewed from the living room. Even if they threw stuff from the house's front, the roof extends too far out below two smaller upper windows. Everything would land on the roof.
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)
Scenes from a Barbecue - S3-E24
Continuity mistake: Becky went from having long hair throughout this season to having very short hair in the last episode (ep. 23), then back to long hair in this episode (ep. 24).
Suggested correction: I'm not sure what the ruling on these types of mistakes is, but "Dances with Darlene" (ep23 and production code 425) was aired out of order. It was the last episode filmed in the season and meant to be a season finale, but aired prior to "Scenes from a Barbecue" (production code 423). One reason seems to be this is a Mother's Day episode and aired on the Tuesday before Mother's Day, and the next episode was Jay Sanders' last appearance.
The Pied Piper of Lanford - S3-E25
Continuity mistake: In Ziggy's first appearance in the series (S2, EP. 16 "Born to Be Wild"), he says he has two kids. He states "I had to make mine. I checked them at birth, they're boys!" However in his second appearance in the series here, he states they were his girlfriend, Jill's, kids and the kids are back living with their father.
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 the girls are at the Lobo Jackie has a long scarf in her hair that moves between having the length of the scarf behind her back and then draped on her front left side.
Visible crew/equipment: In a scene where Darlene and Becky are in the kitchen, you can see the microphone above them for a couple of seconds.
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.
Halloween IV - S5-E7
Plot hole: Just before Roseanne arrives at the Lodge Halloween party, Fischer is holding a small object in his hand that he slightly adjusts to a certain position. Roseanne then unexpectedly arrives dressed as Lady Liberty. When she raises her torch and asks someone for a light, Fischer immediately flicks on the cigarette lighter that he was already conveniently holding and ready to ignite for no apparent reason.
Other mistake: After the crazy guy threatened Roseanne when she was working alone at the Lunch Box, Dan wanted to teach her and Jackie how to use a gun for protection. Dan seems to have forgotten that Jackie was a cop for the Lanford Police Force and already is trained in firearms use. He regularly saw her in uniform with a sidearm.
Visible crew/equipment: While Darlene is at the jail to post bail for Dan, when she says, "I guess I should prepare you for all the things that have changed," the boom mic casts a shadow on the wall, at the right side of the screen. (00:04:25)
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.
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)
Audio problem: During the phone conversation with Darlene and David, you can hear the audience laughing following a line from David. The scene then cuts to Darlene's end for a moment. When we cut back to David, we hear the end of the previous laughter.
Altar Egos - S6-E25
Continuity mistake: When Roseanne and Dan are at the kitchen sink discussing whether Jackie is or isn't in love with him, Dan's robe blatantly switches from open to closed.
Visible crew/equipment: During the final scene, a boom mic is at the top of the screen in the first shot for 1 second.
Visible crew/equipment: In the final scene, at the start of "Lunch Box Girls", a boom mic is seen at the top of the screen for 1-2 seconds.