This is really more of a general question, but given that it is about entertainment matters…
I’m just wondering how the casting process in TV series works. In particular, groups of actors seem to appear in the same groups of shows. For example, Law & Order and Oz seem to have a very high cross over of actors. I’m watching Lie to Me at the moment, and noticed that one episode has multiple actors from the Shield. What strikes me as even odder is that I am almost to the end of the second series of Lie to Me, but I haven’t noticed this before - it seems to be only this individual episode that is populated with the cast of the Shield.
The Law and Order shows are shot in New York, so you are drawing from the pool of Broadway actors. They also need a large number of actors to show up for one scene and then are never seen again. If a particular actor works well in one episode, they will probably call him or her back for another.
Oz is also shot in the NYC area, hence the crossover.
I actually saw a bio of one actor in a road show that proudly said, “No Law and Order.”
Sometimes the executive producer or creator of a show will use actors that he or she is familiar with on multiple shows. Joss Whedon is pretty well known for this, for instance.
In other cases, it could be stunt-casting. There was an episode of Psych that was a parody of Twin Peaks that used many of the actors from the earlier show as guest stars.
There was an interesting graph (of the nodes and lines variety) showing the crossover of casts between all HBO shows. Obviously there was a lot of crossover between the David Simon-produced shows, and Oz crossed over in to just about everything.
Directors and actors like to work with their friends when possible. Why risk some new actor who could be horrible or a diva or psycho nutcase when you can throw a few bucks to an actor you know?
Law and Order (and the multiple spin offs) have filmed a gazillion episodes. As an actor in NYC, if you can’t get a role on that show, you aren’t trying. David Kelly of Ally McBeal, Boston Public, Boston Practice, Harry’s Law, Chicago Hope, Picket Fences, LA Law - has always preferred to work with actors who have been on his shows before.
I would call it smart - cast people you have worked with before, and you have one less problem to deal with later in the filming. Plus, it is a lot easier to simply go through your Rolodex and call a few people than spend hours in auditions with new faces.
Is it fair to new actors? No. But for other actors who have mortgages to pay and are between films/TV series, it is steady work and greatly appreciated.
There are a lot more actors in New York than the ones who might appear on (or off) Broadway. Besides the legit stuff like the series, there are tons of commercials that film in New York. Plus, the skills needed for TV close up work are not necessarily the same as the skills needed for the stage.
No one mentioned the role of the casting director, which I think is the answer to this question. Casting directors cast the minor roles, and screen the candidates to a few given to the director for more major roles. Casting directors work with agents directly, and will often work on several shows. Like in any other endeavor, reliable performance is often more important than flashiness. A casting director is going to like working with agents who send people who match requirements for the part and who will not screw up on the set. If the casting director knows that an actor is reliable, that actor is more likely to get a job than an unknown. This is nothing new. I’ve been watching “Have Gun will Travel” from the late 1950s, and several actors show up in several different roles there too.
Producer Don Bellisario likes to use the same actors throughout his world, which includes NCIS, NCIS: Los Angeles, JAG, Quantum Leap and Magnum P.I. among others.
Mark Harmon, who has a producer credit on NCIS, has brought in his buddies from Chicago Hope, notably Lauren Holly and Rocky Carroll.