Regarding the Klingons appearance. I believe it's the product of genetic engineering. The Klingons pride themselves on being great warriors, and if an operation could make them better at that, I'm sure they'd take it. Now Klingon scientist could of been researching the idea during and before the time of TOS (though I've never actually seen a Klingon scientist, I'm certain they must have some). So by the time of Star Trek:TMP many Klingons may of gotten the genetic operation, and possiblibly even some had it during TOS only since they weren't shown very much doesn't mean it's totally impossible that some Klingons would have the bumpy foreheads. So anyways, as time passed on throughout the TOS movie era more and more Klingons got the operation, and because it changed the DNA code of male and females it would be passed on and inherited by their offspring and he or she wouldn't need to the operation. This would therefore make it no longer neccessary because every Klingon would now naturally look as they do now. My explanation also can agree with how Kor, Kolath, and Kang had the current look in DS9, because they too got the operation. Arne Darven, the Klingon spy from "The Trouble with Tribbles" and "Trials and Tribble-ations" was shunned from Klingon society and kept his human appearance feeling too ashamed to go back to his natural Klingon look. Now if they taken away his human disguise, I think it would reveal the original Klingon look since he never received the genetic treatment.

Well there's my explanation...and a very long one too.

Hobbes
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