When Brian pushes Stewie's crib out into the hall, it bounces off the wall, down the stairs and out the front door which opens to the outside. Even if Brian had left the front door ajar, the door's hinges are on the inside so it could not pushed open that way.
Whenever Brian runs into Rita's house, the walls are blue. A couple seconds later, the walls are yellow and a brown wood.
When Brian is looking at the picture of Rita when she was a little girl in Washington D.C., he comments that the flag in the picture is missing a few stars. However, if Rita is 50 years old at the time this episode takes place (2009), that means she would have been born sometime in 1959. As she appears to be at least 5 years old in the photo, the number of stars on the flag would have been the same then as it is today, as the 49th and 50th states (Alaska and Hawaii, respectively) were both added to the Union the same year Rita was born, 1959.
At the end of the episode, Rita tells Brian to leave her apartment keys on the davenport (sofa). But a couple of earlier scenes clearly shows she lives in a house.