It's worth pointing out that Gastly and Haunter indeed weigh about .2 lbs, but for some reason Gengar weighs a huge amount more than they do. It's really weird, and I almost wonder if it wasn't originally some sort of error since Gengar really doesn't seem that much more substantial than Haunter...Edit: Oh, and Clefable is 4'03'' tall an weighs 88.2lbs, while Gengar is 4'11'' tall and weighs 89.3lbs. Kind of weird for a shadow to be heavier that it's physicall counterpart, don't you think?
They're really inconsistent with the weight of Ghost-types, come to think of it. One one hand you have things like Gastly/Haunter, the Misdreavus line, and most first-stages, on the other you have things like Gengar, Dusknoir, and Spiritomb (why does it weigh almost 250 pounds? Even if they're counting that rock it comes out of, that's still excessive).