Continuity mistake: When Doug, Carrie, Deacon and Kelly are looking at the damage caused by the accident, the same kid in the black and red hat checking his watch walks by twice. (00:05:10)
Continuity mistake: In this flashback episode, when Doug is shaving his mustache and talking to Deacon by his locker at IPS, Danny Heffernan's name can be seen on a locker. At this time, Danny was not working at IPS.
Continuity mistake: When Doug sits down to read his book, he has his book on his tray. This then disappears as the shot changes. (00:11:20)
Continuity mistake: In the scene where Arthur is on the phone with PBS to complain about getting a "Civil War Series" box set, the actual set of tapes changes drastically. When it's on the table and when Carrie brings it over to the counter its a pretty large, has an American flag motif, and says "Civil War" across the top. When it cuts back to it sitting on the counter its a much smaller box with a plain design and says "The Great War" along the bottom. It's obviously a different set, not just the camera angle. (00:14:40)
Head First - S1-E6
Continuity mistake: During the poker game, Arthur teases Spence because he's a virgin, which is mentioned later when Doug tells Cariie, "He teased him about the virgin thing." But in one of the later episodes, it is mentioned that Spence had an affair and had sex with his Home Economics teacher when he was very young and had long hair.
Soft Touch - S2-E22
Continuity mistake: At the beginning, when Carrie is trying to park the car she's wearing a 3/4 sleeve blue top in the closeups, but in the overhead shot of the car for the last attempt when Carrie says that she's cutting it, the driver is not wearing that blue top, the driver is wearing a plaid shirt. (00:01:00)
Mammary Lane - S5-E5
Continuity mistake: At the beginning of the episode, the establishing shot shows a bowling alley with a sign that reads Mar Lin Do Lanes. A few minutes later, Doug welcomes Denise on behalf of the family at Bowl-O-Rama. (00:04:10)
Continuity mistake: When Doug and Carrie are in the living room talking about Doug not going out with Kelly again, he has the phone in his hand, gets upset and throws the phone down. Then Carrie is going to call Kelly for Doug, and when she goes to pick up the phone, it's placed perfectly back on the hook when it should be hanging near the floor from the way Doug threw it.
Continuity mistake: The box of Sgt Salty cereal alternates from open to closed between shots when Doug and Carrie are talking. (00:13:30)
Continuity mistake: When Doug, Carrie, Deacon and Kelly are at Coopers, the man in the blue shirt who is talking to the women sitting at the table behind them appears, disappears, walks off and then reappears again during this scene. (00:08:20 - 00:10:40)
Continuity mistake: When Deacon and Kirby are at Doug's the house over street is a mid terraced house in one shot, and an end terrace in another. (00:06:00)
Tank Heaven - S6-E21
Continuity mistake: In the scene where Danny has just taken the "nucleus" nacho chip, after Carrie walks in, the chip in Danny's hand keeps changing between shots, then disappears altogether almost instantly and his arms are folded when he begins his next line. (00:02:30 - 00:03:25)
Queasy Rider - S2-E1
Continuity mistake: When Arthur starts telling Doug about when he had a bike, you can see the tv gets switched off. However neither Doug or Arthur turn it off as both of their hands are in screen and the remote is on the table. (00:14:30)
Fixer Upper - S1-E12
Continuity mistake: In "Richie's Song" Doug asks Spence if the M&Ms Spence found under the seat in the car are regular or peanut, Spence answers peanut, and Spence then eats them. In this episode, Spence somehow isn't allergic to peanuts. (00:08:10)
Continuity mistake: In front shots of the house you see that the garage is in the front and opens to the street, but the garage door is behind the house entirely. It seems to open in a back alley or private entrance way. The way it is shown in establishing shots, it can not be open to the front street at the front of the house.
Continuity mistake: In many episodes, scenes are shot on the front porch. It is often shown as a large porch that spans a great deal of the front of the house. But shots of the house exterior from a distance show a small set of stairs with very little space near the door. This isn't a porch on the back of the house as it has been shown to only be door to a small yard.
Continuity mistake: When Doug first enters the gym, you can see a price tag hanging off of the front of his weight belt. In the shots following this, the price tag is gone. (00:11:10)
Queasy Rider - S2-E1
Continuity mistake: When Doug tells Carrie that he is getting rid of the bike, Carrie has got a fag in her hand and her hand is up by her head. Camera cuts and now her arm is down across her lap. (00:15:40)
Suggested correction: Spence did have sex with the teacher, but the episode with the teasing at the poker game, Arthur and the guys don't know about her yet. Therefore, to their knowledge, Spence is a virgin, and for some reason, he decides not to defend himself with the teacher story.
The episode with them playing cards wasn't the only season 1 episode where Spence's virginity had come up. In season 1, episode 12, Carrie fixes Spence up with a coworker. When Richie and Doug tease him that they've already been together a month without sex they say: "Do you believe this guy?" "A month, huh?" Spence replies: "Yes a month! A month is not that long not to have had sex." To which Doug says: "Yeah, but if you add in the other 31 years, I'd think you'd be a little antsy." Also a little later in the conversation, when Doug tries to convince Spence that he and the girl have sex in his garage: "I'm just saying, if you wait too long, this opportunity could go bye-bye. Then it could be, hey, another 31 years before this opportunity comes again. It's pretty tough losing your virginity when you're 62." So Spence later already having lost his virginity in high school is a continuity error that they just overlooked and alas instances like these become apparent pretty often when you rewatch the show (like Carrie becoming an only Child, Arthur being said to be a great piano player in a season 1 episode while he can't play a single tune in a later season etc., etc).