My kid is a little older (8), so I don't know what is happening for K as far as TV shows. Also, he rarely watches TV unless he's sick.
We have watched Cyberchase a few times. It is about a bad guy who is trying to take over the world (or something). The kids in the show have to foil his evil plans. To do so always involves some sort of math stuff: working through fractions, making a graph, etc.
Not TV, but have you looked into brainpop.com? It's filled with short videos about all kinds of subjects. Some information is presented and there is some humor, and then if the kid wants to, he can take a little online quiz. It's a subscription site but there is a selection of videos that can be watched for free.
There is also a junior version; some of the topics on the regular brainpop (which is designed for upper-elementary through middle school, I think) are questionable for younger kids. I was fine with it, but would advise you to look through the site yourself thoroughly before unleashing your kid there. Some topics (i.e., Adolf Hitler, AIDS, etc.) may be ones you want to tackle with him first before he watches the BP videos. Most of the topics are fairly innocuous, though.
Best,
Tara
