In Star Trek VI: The Undiscovered Country at about the 21-minute mark, two Starfleet Security officers are guarding the transporter room door when the Klingons transport over to talk with Spock and crew about the assassination of the Klingon High Chancellor Gorkon and arrest of Captain Kirk. You can hear one of them say, "You know, only top of the line models can even talk." What does this mean? Is it a misunderstanding by the legendary stories that surround the Klingons (i.e. just misinformation because they don't interact much with each other at this point in canon), or is it alluding that Klingons used clones for soldiers at some point?
The two crewmen are just sharing some nasty rumor that they have heard about the Klingons. The exact details of the rumor are unclear. We do not know whether the men have actually heard that the Klingons are manufactured (or cloned)—thus there being "top of the line models," in contrast to cheaper and more primitive ones. Or they might not mean "top of the line models" literally, but they have heard that only the leadership class of Klingons is intelligent enough to speak or is allowed to speak. These kinds of racist stereotypes about Klingons play on the way Klingon warriors are often shown to be taciturn and often silent.
The narrative purpose of this scene is not to reveal something about the Klingons—or even, really, anything specific about whatever rumors humans might have heard about Klingons. Instead, it is foreshadowing that those two characters are quite virulently prejudiced against Klingons. The brief conversation between the two men actually occurs when the Klingon leaders initially beam over the Enterprise to dine with Kirk's crew—well before the assassination. The scene is foreshadowing that these two crewmen are actually the assassins!
Lt. Valeris breaks up Burke and Samno's conversation and tells them to get busy:
CREWMAN #1: They all look alike.
CREWMAN #2: What about that smell? You know only the top of the line models can even talk and....
VALERIS: You men have work?
CREWMAN #1/#2: Yes, ma'am.
VALERIS: Then snap to it.
It is very unlikely to be caught on a first viewing (and I certainly did not pick up on it until I knew that Valeris was one of the conspirators), but Valeris is instructing the pair to prepare for their upcoming assassination job.