Other mistake: In this episode, they have a leak in the roof. Yet, the house is a two story house with an attic. So it should not be able to leak into the living room. Also, when Carl and Eddie go up to fix the roof, Eddie falls through the roof and ends up on the living room couch. Again, two story house with attic. Should not happen.
Revealing mistake: When Steve and Carl fall through the roof of the Winslows, there are 3 flies on the camera for approximately 6 to 8 seconds then they fly off when the camera moves.
Continuity mistake: When the family arrives home from the bowling alley, it is dark and pouring rain. After the kids go to bed, Carl and Harriet go to the kitchen and talk. If you look out the windows, it's daylight.
Continuity mistake: Laura meets a guy named Ted supposedly for the first time. He is selling candy bars around the neighborhood and happens to knock on the Winslow family's door. Laura goes out on a date with him. However, Ted and Laura have already had several interactions, and have already dated and broken up in previous episodes in season 4.
Other mistake: When Carl is trying to teach Urkel how to swim in the pool, the pool signs say 4ft and 6ft. But if you notice, when they stand up, the water is only at their wasteline. Obviously, Carl and Urkel are not 8ft tall or anything. So they are not standing in actual 6ft of water.
Other mistake: Eddie drives the car through the front door. This shouldn't be possible. Whenever the front of the house is shown, we see that the porch is several feet above the ground and the only way to get to it are steps that aren't wide enough apart for a car to drive between them.