The thing with the retarded girlfriend...It wasn't that it was in bad taste (which a lot of the usual nay sayers complained about) it was just that it wasn't done very well...It wasn't convincing, or very interesting, or very funny. When you've got a character like Buster, or even GOB, who are clearly slightly mentally retarded anyway, a slightly dull girl who says very little doesn't really make any kind of impact...
One of my favorite scenes in the whole thing is possibly when GOB is trying to blag he knows his wife's name when Michael challenges him and just comes up with "Crindy"...and Michael says "She's not called Crindy" so he looks at the paper and reads out the lawyers name instead....And then when he sees her later, he reads her US Army tag and says "hello.....ooosarmy".
..I mean with that kind of shit, a girl who says slightly dim things isn't going to be that interesting.