Penny is my favorite. Doubtless some of this has to do with the mysterious charms inherent in a healthy 20-year-old female, but I believe it is also about how the acting talents of Kaley Cuoco are put to use. She has the amazing ability to transmit what her character is thinking through facial expression.
There is a scene in which Amy Farrah Fowler (played by Mayim Bialik who used to play Blossom) who was NOT Sheldon’s girlfriend asks Penny if she considers herself a slut. Penny responds, “I’m not a slut,” but in doing so, she pauses. You can see her consider the notion.
Penny is opposite of Sheldon. To Sheldon, knowledge of science and all that is academic comes naturally while he has to study his way through even the simplest social interaction. Penny is a natural people-person who is untutored in academics.
In spite of Penny’s many charms, the show is, of course, centered on the scientists but, and this is the important insight, not the science. The science is there as background to the study of the characters.
As an academic, at some point I came to the realization that I got most of the picture I had of the world through books and other media and —this is the important part — books are not the same as reality.
Books are a sketch, a photograph, at best a statue. While these are all good, even a statue of Venus is not the same as being with her.
This is true of academics from the arts, the humanities, and the social sciences as much as the sciences, but each has its own flavor.
(Cheers did a good job of showing how this is manifested in the arts and humanities with the Diane character.)