This was originally posted on my Dreamwidth.
Hey. Let's talk about hair in Yu-Gi-Oh! Duel Monsters.
Most YGO characters actually have pretty tame hair! Yes, a lot of it looks kind of wild, like Duke's and Tristan's, but it's pretty legible. By this I mean that their hair is stylized, but it's clear in every case what that stylization is meant to express. (For another example to explain what I mean by this: you understand that the Powerpuff Girls are supposed to be human girl children, despite their features being extremely simplified and abstracted from what human children actually look like.) Duke has black hair in a ponytail. Tristan has a brown pompadour. Joey is a delinquent with big bleached hair. Their hair is out there and sometimes sort of silly-looking but you can mentally translate it into human hairstyles pretty easily-- and even more easily if you know that IRL yanki kids do even wilder stuff with their hair than these YGO ones. In fact, YGO has very few characters with unnatural or wacky hair colors! Note that there's just black, brown, blonde, and silver above. This isn't to say that they don't exist -- especially in later seasons -- but as far as recurring series staples go? Nope. This is unusual for anime, especially a colorful wacky fantasy shounen. It's a lot more common in genre stuff for the main cast to be color-coded. (BNHA, One Piece, Fairy Tail, Sailor Moon...) Usually this kind of limited hair-color palette would be more characteristic of something more slice-of-life-ish, like Haikyu!! -- sticking to mostly natural hair colors helps to keep the series grounded in "reality" by removing a level of abstraction & fantasy from the art. Out of the above spread of characters, the ones with the least "natural"-looking hair are Pegasus, Bakura, and Marik. Evil-Marik and Evil-Bakura have more fucked-up-looking big hair than their less evil counterparts:
So! Setting aside characters who aren't actually important to the plot of YGO (Zigfried Von Schroeder & Mako Tsunami, for example...)... The characters with the actual "wild and crazy anime hair" are all characters who have Millennium Items. What I am suggesting here is that the characters' hair being wacky is actually thoughtful character design on the part of the YGO creators; central characters with "unnatural" hair are intentionally designed to be fundamentally distinct from the normal people around them. Pegasus's is the most normal; his hair is gray, which is a human color for hair to be, and it's not an especially weird shape or anything... and his Millennium Item has no evil spirit contained within it. He's a normal guy who had his Millennium Item forcibly jammed into his skull. Marik is a close second; his hair is pretty tame, and his Millennium Item also has no evil spirit contained in it. Yami Marik, however, is a secondary personality that was created in response to the extreme trauma Marik experienced as a child. That doesn't sound terribly magical, until you take into account that the traumatic event which precipitated the creation of "Yami Marik" was a semi-religious ritual in which his father carved Atem's name and life story into his back. The carvings in his back are the only piece of the Pharaoh's past & identity left in the entire world; the rest of Atem's "self", and all record of his existence, has been completely erased. The Pharaoh's real name, Atem, is a key component in an enormously powerful spell keeping a massive amount of evil magical energy sealed away from the world; Atem is so immensely powerful that even his name is magic. So-- yes, Marik isn't possessed by an evil spirit, per se, but Yami Marik does have some magic stuff going on. Which brings me to Atem! Pharaoh Atem, possibly the most powerful sorcerer in history, an ancient evil ghost who retains the ability to reach into people's brains and shatter their psyches with his magic powers even after 99.9999% of his soul and magic have been sealed away. Atem is a spirit who is thousands of years old; when he was alive, he was a child god-king with such a thorough grasp of magic that summoning enormous god-demons was a game to him. A game he always won. Like, take a moment to appreciate what the ancient sorcerer-duels were: wizards so enormously powerful that their idea of fun is Pokemon battles with literal monsters. Gnarly. Now think about the fact that Pharaoh Atem, at age sixteen, was such an adept sorcerer that he could summon and control gods to win his wizard fights. DOUBLE GNARLY. So what we've got here is not just a spooky ghost, and not just a divine king blessed by the gods being a spooky ghost, but a divine king blessed by the gods who is also THE MOST MAGICAL PERSON WHO EVER LIVED and is thousands of years old being a spooky ghost. 
Atem is an eldritch horror. He's not really anything; he's not a monster, but he's definitely not human. He was at one point, but I think after maybe a thousand years of being a disembodied evil ghost with immense magic power and no sense of self whatsoever you stop being that and start being Something Else. The Pharaoh is an ancient magical spirit whose very presence bends and warps reality; he is a thing that should not exist. He is neither dead nor alive, not human or monster, not god or mortal. He's not exactly a ghost-- Pharaoh Atem never died-- but he's not not a ghost. I feel like you really have to remember that Yu-Gi-Oh is a story about a boy making friends with the evil ghost living in his body. In the beginning of the first season of Duel Monsters, Yugi doesn't quite realize that he's been possessed by a spirit; the realization dawns on him slowly, as the Pharaoh's actions puppeting Yugi's body stop being things that Yugi himself would actually do, culminating in a duel in which Atem very nearly just murders Seto Kaiba. Yugi has to forcibly wrest control of his body back and spends a while sobbing uncontrollably on the ground and then another while in a silent horrified daze as he struggles to comprehend what the fuck is actually happening to him. But I digress; back on point. Atem is an eldritch horror and the most magical person on the entire show... and his hair is also the wildest. Not only is Atem's hair wild, but as I mentioned earlier it is almost impossible to even communicate. What color is it? What shape? What does it represent? Most anime hair, as I mentioned earlier, is clearly an abstraction of something; it is exaggerated, but there's no exaggeration without something to exaggerate. You know? Everything exaggerated is an exaggeration of something. But... what is this an exaggeration of? How do you draw that? It can't be further abstracted or really reinterpreted in any art style that isn't the YGO art style; since it's so unclear what the abstraction is meant to represent, it's impossible to represent it in a different style without risking making it too different and thus unrecognizably Atem. It defies comprehension, and thus it defies description and reinterpretation. How would you describe that hair in words? What would you say Atem's hair color is? ...I got nothing, and neither does basically anyone else. I have never seen any description of Atem's hair that accurately actually conjured up an image of what his hair actually looks like. It's not really that complicated, but... it's something. In other words:
The Thing cannot be described—there is no language for such abysms of shrieking and immemorial lunacy, such eldritch contradictions of all matter, force, and cosmic order.
This, finally, is my point. Pharaoh Atem's hair is like that on purpose. He is a Lovecraftian eldritch horror. You look at him and your human mind cannot actually comprehend what you're looking at. You can't describe it or represent it. It is an exaggeration without an original point, an abstraction of nothing. The Millennium Puzzle drives people mad; the inside of the Pharaoh's mind, as it manifests inside of the puzzle, is an elaborate labyrinth of optical illusions. Those are both canon facts about the Pharaoh. What the incomprehensible wacky hair represents, then, is Atem's inhumanity, rather than an actual hairstyle.