I have never been a fan of mid-series flashback and/or series update episodes where they catch you up on who all of the characters are and why they are the way they are. Usually, they come in the season premier as a tool forced upon the producers by the networks as they try to re-claim viewers that have faded off or acquire new fans. The problem with it is that they never really work and come across very awkwardly, particularly to loyal viewers, who experience them as an annoyance.
One of the few exceptions to this, however, is the NCIS episode Truth or Consequences - the opening show of season seven (rebroadcast aired early this evening on USA). There is a little awkwardness as they attempt to showcase who all of the characters are, but the fact that it is coming from an interrogation makes it more natural as part of the story.
