Thanks for all the great comments on “Dumbening.” This is apparently something a lot of us have noticed.
In comments, Mark Farrell suggested a parallel thread on characters who got smarter as the series went on, and rightly suggested Margaret on M*A*S*H as an example. She and Frank started out at around the same level (Frank was a little dumber than she was when the show started, but not that much, because he was originally intended to be a good surgeon) and then she gradually got smarter while he constantly got dumber. And then after Frank left, she continued getting smarter and more sympathetic until by the end of the series, nobody had called her “Hot Lips” in years.
Other characters who got smarter as the series went on? This is obviously a lot tougher to find than characters who got dumber. Making a character dumber is almost an unconscious process, especially in a comedy. Making a character smarter is usually a conscious decision, and writers can rarely make it seem plausible. Remember how 24 tried to make Kim smarter (a CTU agent, yet) in the third season, and how nobody bought it? Another example of that is Theo on The Cosby Show. The whole point of the character originally was that he was a poor student. It would have been logical for him to improve as time went on, but as I recall, the writers didn’t really make it seem logical; it just felt to me, at the time, like suddenly he had gone from a slacker to a smart guy without a clear transition. It was part of Cosby’s attempt to make all the kids perfect so they could all be role models for the world. I just didn’t buy it.
There are also characters who transition very early on into being smart, but that’s more about the writers finding out who the character is. Lisa Simpson was not particularly smart in the Tracey Ullman shorts or some of the early episodes, but by the end of the first season they had established that she was the smartest one in the family, and they stuck to that characterization after that. (Her intelligence has fluctuates since then, but she’s remained the smartest Simpson with the possible exception of Maggie.)
As others pointed out, Edmund Blackadder got smarter: Prince Edmund in the first series was an idiot, while subsequent incarnations of the character were P.O.’d at being surrounded by idiots. But it’s debatable whether Edmund should be considered one character who develops over time or a bunch of different characters with the same name.
Corky on Murphy Brown may be a character who got smarter in a plausible way. She became more competent and less ditzy as the show went on, the way real-life people get more competent and knowledgeable as they get more experience. And Edith on All in the Family (who, by the way, was much smarter in the pilot than she became later; originally she was going to be closer to the deadpan character from the original British version, but they quickly decided to make her more innocent and sweet) also seemed to get smarter, though you could argue that since she was never really dumb, she didn’t so much become smarter as more assertive, more willing to challenge the other characters.
Sometimes a show will try to make characters smarter in a gradual way, and then kind of give up on it. In the middle of its run, King of the Hill tried to make both Bobby and Luanne smarter, Bobby by aging him a year and making him act a tiny bit more grown-up, Luanne by switching her from beauty college to regular college. Both those characters have now regressed to the point of being even more clueless than they were originally. And of course every time The Simpsons tries to make Homer a little smarter, they give up within a few weeks.
Tracy on 30 Rock may be a character who has smartened up as other characters have gotten dumber. He’s still not exactly sane, but whereas in the early episodes he was not merely an idiot but a dangerous idiot (“I am a stabbing robot!”), the show has humanized him a bit, given him occasional lucid moments, and even made him a genius video-game creator. I wonder if other Token Dumb Guys get a little smarter as everybody else on the show becomes dumber?