From inception, Star Trek's radical act of difference was to insist that difference need not be a radical act. "We will find it impossible to fear diversity and to enter the future at the same time," Gene Roddenberry once said. His vision for a truly egalitarian future remains just as daring today as it was in the 1960s.

Whether they're grouchy or graceful, these physicians help the heroes of Star Trek accomplish their space-faring missions.

I love seeing Dr. Crusher on TNG, but she is not the only doctor. For her one season, I think Dr. Crusher's replacement is totally worth the watch.