Continuity mistake: Carrie is holding her baby sitting on the couch. Left hand holding the baby, right hand holding the baby's left hand. Then it cuts to a different angle, Carrie's right hand is in the baby's lap and her left hand is on the baby's back. (00:32:50)
Continuity mistake: Carrie Matheson leaves her sister's house in a Jeep Compass with her daughter. When she arrives at her destination, she is in a newer model of the Jeep Compass (the front indicators are different).
Chosen answer: Everyone else calls him Brody or Sgt. Brody, and it probably became habit to her.
The_Iceman
Can't get the source but I read that even the Producer responded to that. Stating that it was common practise for a military wife living in a military complex as everybody refers to their husband by their last name.