I was looking at reading the "Simpsons: Beyond Forever" book, and I think i *may* have found the origin of the phrase "insensitive clod"...
There's this one episode where Lisa takes tap dance lessons, but really sucks at dancing, so she doesn't get a part in the dance recital. Professor Frink (the geeky scientist guy) gives her a pair of self-tapping shoes, and she goes in the recital and totally brings down the house until the shoes go crazy and she scares everybody out of the recital hall. After, Lisa feels bad that she really didn't dance that well and it was only the shoes, so Professor Frink lies and says the shoes were really in the "off" position and she actually did dance all by herself, but Homer shows the shoes, clearly in the "on" position, to Lisa, and Professor Frink says to Homer:
"I was just trying to spare the little girl's feelings, you insensitive clod!"
so...i think that's where it's from. If this is common knowledge and I'm the only one just learning this now, or if I'm wrong...
don't spoil my fun, you insensitive clod ;-)