If you notice, in the scene where the "Cheap Girls" comes to the house to talk to Walter about changing their name, they did not originally say that they wanted to change it to Meryl Streep. If you read their lips they do not say Meryl Streep. Long after the voiceover has stopped saying Meryl Streep their mouths continue moving. Wonder what the original name was?
At the train station Walter and Anna decide to buy the house and the train comes barreling through the station. This should have caused a noticable change in the pitch of the train whistle. This is called the doppler effect. Alas, no doppler effect can be heard.