While the drastic redesign of the Klingons was a departure from previous Star Trek incarnations, the way they sounded also changed. There was a vocal effect added to make them sound more alien.
Did they change the Klingon language in Discovery?
Supposedly the Klingon spoken in Discovery is more accurate to the Klingon language constructed by Dr. Marc Okrand beginning in the 1980s. Previous incarnations of Star Trek have used that language, but tended to play more fast and loose with pronunciations and rules in the language.
Most notably the make-up of the Klingons was modified for TMP. In TOS their foreheads were flat exactly like those of humans. The only distinguishing mark was their beards. In TMP and thereafter, however, the Klingons had ridges on their foreheads, to emphasize their being alien but probably also their martial nature.
The official explanation is that Klingons normally have hair but completely shave it off during a war. Pronounced. The DIS make-up includes cheek prosthetics.
Attempting to replicate experiments by humans to create augmented soldiers, Klingon scientists used genetic material from human test subjects on their own people, which resulted in a viral pandemic which caused Klingons to develop human-like physical characteristics.
The Terrifying Secret the Q Don't want you to know
Why does Worf look different?
After season 1 of TNG wrapped production, Worf's facial prosthetics were either lost or stolen. This presented Michael Westmore, TNG's primary makeup designer, with an opportunity to improve the look of the character.
Worf is an outsider to Klingon society, marked as different both by his positionally — adopted child of humans, member of Star Fleet — and by his unshakeable commitment to the values that Klingons espouse.
In Star Trek VI: The Undiscovered Country (set around 70 years before the Next Generation era began), Colonel Worf (also portrayed by Dorn) appears as the legal advocate of Captain James T. Kirk and Dr. Leonard McCoy after they are accused of killing Chancellor Gorkon of the Klingon High Council.
The redesign of the Klingons almost from scratch for Star Trek Discovery is the arguably most controversial artistic decision in the history of the franchise. Whether they criticize the new look and feel of the species for its clumsiness or for its disrespect of canon, many fans genuinely dislike it.
In Star Trek III: The Search for Spock, Kirk's son David Marcus was killed by Klingons, and it hardened Kirk's heart. He hated Klingons for it and was furious when Spock set him up (three movies later with Star Trek VI: The Undiscovered Country) as the escort and emissary for Klingon Chancellor Gorkon.
It's never outright explained in canon, but given that the Klingons were conquered by the Hurq a long time ago and they were not apparently native to the Klingon homeworld, they would have needed warp drives to accomplish that. So presumably they stole the tech from the Hurq.
Being descended from DNA molecules planted by the Ancient Humanoids, Klingons are distantly related to the other humanoid species of the galaxy such as Humans, Romulans and Cardassians, even though each evolved independently on their respective homeworlds.
Very simply they look different for the same reason that the Klingons on The Next Generation, Deep Space Nine and all the later series made them look different: Modern makeup is much cheaper and easier to apply than that used in the 1960's.
Why do Klingons look different in Discovery season 2?
Star Trek: Enterprise conjured the Augment Virus to justify the changes to the Klingons, but Star Trek: Discovery's revamp of the Klingons never got any kind of explanation. It was merely hinted, as the Klingons grew their hair out in Star Trek: Discovery season 2, that they would eventually look like TNG's Klingons.
The Changeling Martok was a Changeling of the Founders in the 24th century. In the 2370s, this changeling was one of a handful agents tasked with destabilizing relationships between the larger organizations of the Alpha Quadrant.
Klingons are known to have sexual relations with humans, with the character B'Elanna Torres being an example of a Klingon-human hybrid; Torres' mother is a Klingon.
Star Trek: Lower Decks season 4, episode 9 reveals that Klingons have pink blood, a departure from their usual red blood. The choice to give Klingons pink blood was made in Star Trek VI: The Undiscovered Country to create an alien look and to avoid a higher film rating.
petaQ. One Klingon term used as an insult on numerous occasions was petaQ (also spelled "Pahtak", "Pathak", "p'tahk", "p'takh", "patahk", "pahtk", "p'tak", or "p'taq"). It was also used by the Klingons of the mirror universe.
Picard was under severe emotional distress, but the crew was unwilling to call him out on it - except for Worf. When he expressed his concerns to Picard, he was called a coward - a huge insult in Klingon culture. Worf became visibly angry, and told Picard he would have killed him if he had been anyone else.
Worf was Married to Jadzia Dax and (spoiler) at her death in DS9 became a widower. He did have a fling with Deanna Troi through 2370, which was the result of Worf seeing himself Married to Counselor Troi in an alternate reality which led him to actually pursue Deanna romantically which was welcomed by her.
Later in the series, she becomes involved with the Klingon character Worf, and they marry during the sixth season of the show. In the sixth-season finale Jadzia dies but the Dax symbiote survives, and in the seventh-season premiere returns with a new host Ezri Dax, played by Nicole de Boer.
The baldric didn't just show that Worf was Klingon. It was also an important celebration of Klingon heritage. While other baldrics might have been used to carry weapons, the Klingon ones were solely for honoring their family or house, something that was important to Worf.
Summary. The appearance of Klingons in Star Trek has evolved over time, with the original series using minimal makeup due to their tight budget. Later series introduced cranial ridges, and Discovery created a more alien look for the Klingons.
In 2357, Worf entered Starfleet Academy. He graduated in 2361 and was commissioned with the rank of Ensign, becoming the first Klingon officer in Starfleet. Although Worf took immense pride and a sense of honor from serving in Starfleet, most other Klingons shunned and belittled his choice of vocation.
