When the lead Cheap Girl tells Walter they want to change their name, you hear "Meryl Streep" but his lips say something else. The same thing for Walter when he tells him he's not changing their name. Perhaps another name was originally used and the producers didn't get the permission to use it.
When Walter's lungs are compressed from falling into the hole with the carpet, trapping his arms, he is unable to shout out to Montgomery Schrapp (plot device).
In the following scene when Anna is searching for Walter, he is clearly able to shout to her.."Upstairs!!" (full Tom Hanks signature shout).
When Walter goes into the den to call the permit man, Montgomery Schrapp, you see a candle on the desk beside the phone. Walter uses a match to be able to see the number on the paper, and the paper catches fire. When Anna gets home and comes into the house, she turns on the light. When she finally finds Walter in the floor in the den, she turns on the light in that room, too.
Initially, the front door swings into the house and the door knob is inside and the handle is outside. They are on the left (as viewed from outside the house). After the door and frame fall off the house it is propped up in the doorway, but the door now swings outward. The door could only do that if it were propped up backward, which it is not: the door handle is still outside and the knob is inside, and they are still on the left (when facing the house from outside).
After the characters have hauled two two-gallon buckets of water up the ladder and dumped them into the bathtub, Walter goes back downstairs and, after the kitchen fire, brings up the third recently heated on the stove. That is also dumped into the tub, causing the tub to crash through the floor and land below. As the camera angle picks up the tub falling through the floor and the ensuing crash and breakage, there is no water spray from the broken tub.
When Carlos says, "Goodbye" to Walter, Sr. and his Brazillian wife, he first says "Auf Wiedersehen!"(German), then tries to correct himself by saying, "Hasta la vista." However he is still using the wrong language, as "Hasta la vista" is Spanish and not Portuguese.