The only time I remember seeing them was when Nick at Nite did a couple of marathons of them.

From what I understand, they just made shows with the same premise over and over, but with different weird characters and different children taken through the looking glass, and the shows usually ran a season or two and were then syndicated with scheduling that just looped the different shows through the same time slot. Land of the Lost ran a little longer. I was kind of interested in that one, because the first season was dominated by big name sci-fi writers, but from what I remember of the episodes I’ve seen they didn’t put much of their mark on it.