The klingons in the original series were quite different (physiologically) from the klingons in TNG. Why?
If you want a spoiler, just say so. If you want to watch the episodes that explain this I'd suggest watching the Enterprise season 4 episodes, Affliction and Divergence. Regardless the behind the scenes "reason" was to make them look more like aliens.
The look first changed with ST:The Motion Picture. Since there was a larger budget, the Klingon makeup design could be more sophisticated than greasepaint and a fake mustache. The Enterprise episodes R. Star mentions will give the in-universe explanation.
To be honest, I think it's one of those things that most fans would have been happy to accept as a "fact of life" - i.e. we all know Klingons look different in TOS because the budget was smaller, but in our minds we're happy to ignore that. Suspension of disbelief. Unfortunately, the (great) DS9 epsiode "Trials and Tribbleations" ruined that - put Worf together in a room with TOS Klingons, and one of the characters is going to say *something*!!! So they had to come up with a canon explanation for it. TBH, I've never watched Enterprise and never will, so I just assume they always had the bumpy foreheads. :P (and just put "Trials" out of my mind)....
They of course ignored the simple explanation - that the Klingon EMPIRE is an EMPIRE made up of many planets and many races.
.... I greatly liked the solution of DS9, by having Worf just acknowledging the differences and still (very grumpily) refusing to explain it I just watched those two eps of ENT for the first time (haven't seen all eps of TOS and ENT). While fine eps in their own right, I don't think such an explanation was 'necessary'. As for real world reasons, I believe I read somewhere that, had they had the budget (and the make-up skills), they would have been portrayed in TOS as less human in appearance as well.
^ I think it would have been hilarious if, during Trials and Tribble-ations, Worf's trip to the past resulted in him immediately appearing as a TOS style Klingon with no one even noticing.
Or: (O'Brien looks at Worf) Miles: "What the..." (Worf whispers to him) Miles: "Budget?..what...nevermind."
Really, that's what they should have done. In TnT they had a chance to solve it, once and for all. They could have just simply ignored the differences and had everyone act as if the Klingons looked the same as modern-Trek ones or, hell, had an introduction by Dorn at the beginning of the episode saying something like this: "Welcome, to Star Trek: Deep Space Nine's episode, "Trials and Tribulaitons." Tonight you're going to see your favorite Star Trek Crew visit the classing original series episode "The Trouble With Tribbles." This landmark episode is a cherished favorite with fans of the series, casual fans and Trekkies alike. When the original series was made in the 1960s they worked on budget and time constraints that didn't allow for the make-up we see and enjoy on television today. This lead to many of the aliens on the show to simply looking human, including the Klingons. It wasn't until the Motion Picture in 1978 that Trek's producers were able to truly bring Klingons to life and give them a look of their own. Tonight we acknowledge these differences but also say that the way Klingons look today are how they always looked, so our crew will not notice these obvious differences. We ask you to imagine along with us that these Klingons always had the fierce warrior look we enjoy and love today. Q'Apala! And enjoy the show!" They could have just had the crew ignore it. Pretend nothing is different. But they HAD to address it, and Enterprise just HAD to try and to explain it. And that created even MORE problems and silliness. The explanation they came up with, yeah, I guess "mostly" works. Still, it would have been far better to never address the difference to begin with. Accept it for being what it is, just the differences of the budgets of the times the series were made in.
That would have been great. Unlike with the Klingons, Trek never bothered to address or explain why TNG-era Romulans had head ridges while TOS-era did not.
Being Spock was able to walk around in public on Romulus without a head ridge, and drew no undue notice, one would just assume some have them and some don't.
Brilliant! I honestly think Westmore was so busy congratulating himself over a cheap way to do the eyebrows that he thought no one would notice. How a once great Hollywood family has descended into hackdom. Anyone notice how old McCoy in TOS was so much more convincing than old McCoy in TNG?
Did you see the test footage of McCoy for TNG? I wish they went with that instead. http://tng.trekcore.com/hd/albums/bonus_s1/sdrevisited_2/tng1_stardaterevisited2_211.jpg