When they are in the bathroom, he says to put your goggles on and then safety first and puts his googles on. Then when it shows him hammering the nail, his goggles are up.
When Carl was in the bathroom, he kicks something at the wall and then the mirror falls and you hear the glass break, but the mirror is still together.
The original cold open to this episode featured Harriette telling Eddie, Laura and Judy to wash the dishes while she gets ready to go to a PTA meeting. After the original airing of this episode the producers replaced it with a new cold open to feature Harriette and Carl sitting at the table and Steve Urkel comes with a robe on saying he was taking a bath, to make it look as if Urkel was on from the beginning. The first season DVD set uses the original version.
The original cold open to this episode featured a scene with Judy, Laura, and Carl. After the original airing of this episode the producers replaced it with a new cold open to feature Steve Urkel tricking Carl out of his sundae, to make it look as if Urkel was on from the beginning. The first season DVD set uses the Steve Urkel version.
The back of Valerie Jones, who played Judy Winslow in the pilot episode, can still be seen in the opening credits at the dinner table scene. It remains that way until the end of the first season.
This actually applies to every episode after this, but since this is the first episode with the new living room I'll mention it here. I know that the house that is seen is stock footage, but it doesn't match the interior. If you look at the porch when someone opens the door, there are a lot of plants, and even a bench. That's not seen on the stock footage. Also, to go down the stairs, you would have to turn left. On the stock footage, there is no real porch. Also, how would someone drive into the garage in the back of the house? The back yard is on the same level as the rest of the house. Also, in the closing theme song when it shows the Winslows at the piano in the living room, the piano shouldn't be at the corner of the house. Remember, the piano was right by the kitchen, so if you go to the right, then you go into the kitchen, which clearly doesn't make sense. The piano should be on the side of the house, or located right next to the door. Also, the stairs to the left of the living room door shouldn't be there, because they go too far over. The exterior shot shows a window there.
The set for the pilot is set similar but obviously different than the design of the following episodes; the front door exits out into a hall; that's clearly seen when Estelle makes her appearance. The makeup of the living room is a bit closer together than the set becomes and doesn't have as many doors off the main room like for the downstairs bathroom that Rachel uses in a later episode. The kitchen is the only set that remains fairly the same when the show moves into the series.