Different Shows, Same People

I just finished catching up to the latest Stargate Atlantis episode. I only today realized that the doctor is played by the woman who plays the engineer in Firefly/Serenity. It has always been a point of interest when favorite actors and actresses would appear in the shows like the Star Trek cast members appearing on either Stargate SG1 or Atlantis. Some have appeared on Heroes, too, and on a few more shows.

I wonder though if in Hollywood, actors are reluctant to take on the roles? Afraid to get type cast? Well, if that's so, they are missing out. As the cast of Star Trek and Star Wars and a whole slew of other science fiction shows can attest, they have careers that last long after the show is cut, simply because the shows are unique and capture the imagination.