It's got explosions, skepticism, humor, explosions, physics, perseverance, biology, and did I mention explosions?
I know the show has been on for, like, 10 years, and it hovered vaguely on the periphery of my consciousness somewhere, but I had never seen it. Then, about a month or so ago, one of my sons asked to watch it, and now the family is hooked.
Mostly the kids like the explosions, and mostly the husband likes Kari, but there is something for everyone. In addition to the complete excitement around physically creating (and, full disclosure, destroying) things, it is great that these funny, compelling people are so unabashedly fond of science and learning. You gotta love a show that on the day one of your kids comes home with a study sheet about Newton's Laws of Motion, that evening they get treated to detailed discussion of the idea that force=mass x acceleration through crashing cars into a wall at various speeds and watching the crumple patterns.