While Carrie is waiting for Brody to arrive at Langley, the camera angles change several times between the road that Carrie is watching, and Carrie herself. During one shot of the road, male and female extras can be seen walking past a monument towards the building, in the next shot they are gone. When the angle changes back to focusing on Carrie, you can see in the reflection of the door that the two extras are waiting to be given their cue to walk.
When Carrie is talking with Brody in Langley, the extras are repeated walking out of the building. When the camera angle changes, repeats the same extras out of the building once they had already left.
Dana and Finn easily sneak into the viewing room at the top of the Washington Monument at night when the monument is otherwise unoccupied. In reality this would be impossible and/or would set off all kinds of alarms.
When Carrie is waiting for Brody in Langley, Brody is reflected in the glass doors waiting for his cue behind the outdoor sculpture.