Over the course of his long life and adventures spanning all time and space on Doctor Who, The Doctor has built up an incredible array of villains, including the Cybermen. They are some of his most persistent foes, first popping up in the 1966 episode, "The Tenth Planet." While their origins have changed a few times over the years, the threat they represent has not. Their desire to convert as many humans as possible into powerful cyborgs to propagate their species is something The Doctor always stands against.
But there are a surprising number of things about these malevolent mechanical monstrosities that just don't add up.
Different Groups
One of the most confusing things about the Cybermen is the various groups that exist. Over the years, different variations of the Cybermen have popped up on various planets and even from other universes. This is in part due to different eras of Doctor Who making changes to their backstory, as well as many other aspects of the series. The end result is a confusing history that viewers either have to ignore pieces of or producers have to retcon to make work.
Still Feel Pain
However they started, the Cybermen always viewed emotions as a weakness. They were just some of the human deficiencies that the cyber-conversion process weeded out. But if the process was intended to make humans more powerful and remove their inherent weaknesses, having them still feel pain makes no sense. It seems like the first thing that should go.
Apparently, the conversion process at least makes its victims not care about the pain but they still feel it. That just seems like a good way to torture someone.
Emotionless, Yet Smug
So, the cyber-conversion process failed at removing pain but was successful in removing emotions. Almost. Some Cybermen were still known to feel and display certain emotions, such as anger. But the one emotion they couldn't seem to escape was smugness. Despite their metal faces that do not move, they all have a smug tone of voice that gets under your skin. The higher up their ranks you go, the worse it gets. It's almost like they didn't want to eliminate that one specific emotion.
Weird Weaknesses
For a race of powerful cyborg creatures, they sure had had some strange weaknesses. They could be damaged by bazookas or lasers, which is fair. The same can be said of high radiation levels. These are the kind of things one would expect to kill an opponent. While it was a little more odd, spraying Cybermen with a strange mixture of solvents called the Polly Cocktail also seems to do the trick. That seems relatively reasonable. Then you find out that the scent of a very specific flower is deadly to some Cybermen. That makes no sense at all, though it's still more logical than the Glittergun.
Glittergun
Of all of their weaknesses, gold might be the most ridiculous. For some Cybermen, all it takes is touching gold to take them out. Gold tipped bullets and arrows were often used, though something even more simple like a gold coin would also do the trick. For many, it was the act of inhaling gold dust into their respiratory systems. This led to the invention of a devastating weapon called the glittergun. As you've probably already guessed, it was a gun that shot gold glitter. It's hard to look like a badass when you're shooting golden glitter around the room.
Cyber Everything
The Cybermen must have picked this habit up while watching reruns of the 1966 Batman show. In that series, the Caped Crusader loved renaming everything with word "bat" in front of it.
A computer wasn't simply a computer. No, it was a Bat-computer. The same can be said for the Bat-phone, the Bat-pole and the Bat-shark repellent. The Cybermen are guilty of this, as well, putting the word "cyber" in front of everything. Cyber-suits. Cyber-Lords. Cyber-Dogs. It was all a little much.
Dog Conversions
Cyber-conversion was designed to be primarily used on human, and other species that were relatively close into design to humans. But the Cybermen didn't stop there. They eventually updated the process to be used on dogs. This wasn't usually a full conversion as the dogs maintained their flesh and blood torsos while their limbs and head became electronic. If you guessed that they were called cyberdogs, you would be correct. In reality, there is not actual need for cyberdogs, unless the Cybermen wanted cute puppy photos they could relate to.
Class System
As strange as this sounds, a group of humans who have, in some cases willingly changed themselves into cyborgs still have a hierarchical structure of sorts. They have different levels of drones, leaders and masters. It's less about organization and more about being some sort of class system, which you think wouldn't matter to a bunch of cyborgs. Yet, it exists in their culture, such as it is. There's no real value to this system to them, so it begs the question of how evolved they truly are.
Survival
Regardless of which Cyberman group or origin story you're looking at, the sole goal of this race is reputedly survival. It could be from sickness or just avoiding death from old age, but they all want to survive. This instinct extends to their entire species as the only way they can propagate it is by converting more Cybermen. But the only goal of Cybermen is to make more Cybermen, until everyone is either one of them or is destroyed. The fact that they have no other discernible endgame is why they keep losing.
Design
The Cybermen are artificial constructs designed and built to preserve whatever is left of the person inside the shell, but theoretically improving on that person in some ways. If the goal is survival through technological advancements, why not make them more technologically advanced? They don't run very well and have a lot of mediocre weapons. They're honestly pretty easy to avoid if you put your mind to it. Outside of their numbers, the Cybermen honestly don't seem to have a lot of physical advantages in most situations.