I really admire THE BIG BANG THEORY. Here's a successful show that could have skated along (Like Two and A Half Men or How I Married Your Mother) for years on a formula. It had a breakout star with Jim Parsons and it could run him to death--like Robin Williams on Mork and Mindy or Michael J. Fox on Family Ties way back when.
But someone somewhere said, "Hey, let's stop using Sheldon in every scene. Let's even stop focusing exclusively on those four guys and one girl every week."
So they brought in three more actresses that have made the show much more versatile. Now we hear conversations between the women, who are equally funny. Turns out these writers knew how to write for women as well as men. They broadened the world on BBT. And guess what, the women are written to be as smart as the men. Perhaps smarter.
What other shows do this/have done it? What shows managed to evolve over time?