Continuity mistake: In the first episode, in DJ's room when Stephanie is crawling across the curtain rod, you'll notice that there is a giant window, and a window behind Stephanie's bed. In later episodes, the giant window turns into a 3-paned bay window, and the window behind Stephanie's bed disappears.
Continuity mistake: On the first floor of the house, there are two staircases leading up to the second floor - from the kitchen and the living room. But on the second floor, there is only one staircase leading down. And it doesn't matter which one they use, they still end up coming upstairs in the same place.
Other mistake: In the opening credits when it shows their house, you can see the garage is located in the front of the house. But when the family goes down to the garage or Joey's room when it was later transformed, they used the stairs all the way in the back of the house to go down to the garage. So that would mean the garage is really big, (which it isn't when you're inside it or its not the same house).