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.
Continuity mistake: After Spence suffers from his allergic reaction to peanuts he's seen lying on the couch. Doug then says something to the effect of having to scrape Spence's lunch off the fence, indicating that he threw up. But the allergic reaction took place before they got to the lunch.
Revealing mistake: Carrie comes into the kitchen, visibly hot and sweaty, and says, "Could it be any hotter?" Doug also has a sweat stain on his back and they stick their heads in the freezer. Suddenly Arthur walks in and says, "Do I have the word pushover on my forehead?" Arthur is wearing a thick shirt tucked into long pants and yet is not sweaty. At his age he would be more visibly drained from the heat than both Carrie and Doug. This happens again later in the episode in the garage.