What are some of your AOT Headcanons?

Here are mine:

I think seeing the future was the Founder's powers, not the Attack Titan's.

  • I think Eren was using the Founder to mentally send back select memories, thoughts, ideas, and emotions to manipulate his past self, past holders of the Attack Titan, and even other Subjects of Ymir (SoY) throughout key points in history.
  • The Attack Titan's desire for freedom is just Eren sending back his own feelings to past vessels of the Attack Titan.
  • Much more details about all my reasoning listed in this post

All three Branches of the Military have their own anthem.

  • The Survey Corps' anthem is a German cover of Shinzou wo Sasageyo!

Hange visited the Marleyan Museum of Natural History at least once

  • Sometime before the Raid on Liberio.

Commemorations of Paradis:

  • The anniversary of retaking Trost became a Holiday on Paradis.
  • The anniversaries to the events of RTS, the original fall of Wall Maria, and the culling operation of 846, all became Memorial Days.
    • Kind of like how Canadians have Remembrance Day.

The reason the book in Historia's flashbacks name Ymir as Christa is because Christa was Ymir's birth name before her village was raided by the ancient Eldian tribe.

  • The Eldians would force the people they enslaved to change their names as both a power play against their victims as well as a method of stripping them of their sense of identity.

The 9 Titans are so imbalanced in power scaling that I think that they weren't split equally between Maria, Rose, and Sina (MRS).

  • Like for example, one daughter got 3 Titans (Beast, Cart, and Jaw); another got either 4 or 5 (Founder, Armoured, Warhammer, and Colossal if just 4, as well as female if 5); lastly, the third daughter got 2 or just 1 (Attack if just 1, and female if 2).
  • When Ymir died, no one knew that the Titan power specifically came from her spinal fluid, so King Fritz had MRS eat their mother's entire corpse with MRS devouring parts of her at random. So the one daughter would have consumed more spinal fluid than the other two, becoming the most powerful, with the weakest being the daughter who ate the least amount of spinal fluid.

The reason "royal blood" is so special is because a monarch at some point in history restricted the Founding Titan (FT) to only their direct descendants.

  • Before that all SoY could use the FT without restrictions.

Founding Titans do not need Ymir for regeneration or the creation of their Titan bodies is done by default—without having to be sculpted in the Paths. Only the other 8 Titans and Pure Titans also have to be personally sculpted by Ymir.

  • Ymir being the first Shifter already had the Founder in herself. She didn't need to have anything sculpted in the Paths to regenerate or create her Titan form.
  • The two daughters of Ymir that didn't inherit the Founder had to be personally sculpted by Ymir to regenerate and create their Titan forms.
  • Eren does need to be sculpted in the Paths to regenerate and create his Titan body by Ymir because even though he has the Founder, it's restricted to him as he is not "royal blood".

Pure Titans only exist because King Fritz had MRS eat Ymir's corpse in the first place.

  • We know that if a Titan Shifter has not transferred their powers on death, it will just manifest in a random infant - so there is a way to pass on the power without cannibalism. If MRS never ate their mother's corpse, the power would have just transferred (without being split at all) to whoever happened to be the first grandchild of Ymir.

Endocannibalism is the cultural practice of consuming one's dead relatives. Ancient Eldia was a society that used to practise ritualistic endocannibalism, but the practise became taboo generations prior to King Fritz coming into power.

  • King Fritz just got the idea to feed Ymir to MRS from stories passed down about his ancestors.

I think the other noble families that can't be controlled by the Founder are SoY that were Titan experiments like the Ackermans.

  • The other nobles are much less powerful than the Ackermans because their ancestors were basically the prototypes that lead to the Ackermans strength.

Several Founding Titans (FT) in history would alter (or try to alter) Eldian biology.

  • One FT had a thing for good teeth, so they got rid of all oral diseases which is why all the Paradisians all have perfect white teeth despite not having access to modern dental care.
  • Several FTs throughout history have tried begging, demanding, threatening, and cajoling Ymir to end the 13 year curse. It was one of the few things that couldn't be altered.
  • Other FTs have tried to make SoY population immortal, but it was another one of the few things that weren't able to alter. One of these FTs got the closest to this goal though by accidentally making Pure Titans immortal so long as their napes were not damaged.
  • The Ackermans themselves used to be normal SoY (they could be turned into Titans, they didn't have superpowers, etc.) before an FT experimented on them.
  • The Titan Powers being removed led to a whole lot of outbreaks in diseases that past FTs had made Eldians previously immune to.

Historically, SoY was a distinct term from Eldian.

  • SoY were specifically Eldians with the Titan gene. However the normal Eldians kept procreating with SoY until everyone in the Eldian Empire became SoY, making the two terms became synonymous.

Karl Fritz created the Wall Titans out of real people.

  • The reason they didn't turn back after the Titan powers were gone is because Ymir never rebuilt their human bodies, so that they wouldn't suffer the rest of the world's wrath after Eren used them in his genocide against 80% of humanity.

After creating the Walls, Karl Fritz also turned a huge amount of his population into Pure Titans.

  • In order to uphold the lie that the world really had been overrun by Titans.

Karl Fritz's mother was a Marleyan victim of Eldian concubinage.

  • Any child of Eldian royalty are eligible for the throne even if one of their parents is a concubine.
  • Most in the royal line don't want to die in just 13 years by inheriting the FT unless they're already in old age and are going to die soon anyway. Its usually royal blood children with a concubine parent that take on the FT because they're desperate to improve their parent's treatment much like Marley has Eldians do.
  • Watching the Eldians treat his mother the way they did is what lead to Karl Fritz's motives.
  • Karl Fritz really hated his family on his dad's side. So much so that when after the collapse of the Eldian Empire and the creation of the Walls, he used the FT to make his royal blooded relatives (half-siblings, aunts, uncles, cousins, nieces, and nephews) into the first batch of Pure Titans to wander Paradis outside of the Walls. The only royal blooded relatives Karl Fritz spared from this were his own children and the royal line that stayed on the mainland.

All the 9 Titans embody a certain aspect of Ymir, her life, and experiences.

  • Female obviously because Ymir herself was a woman.
  • Beast is literal dehumanization, from her treatment as a slave.
  • Founder from her obedience of King Fritz.
  • Armoured from the Eldians' abuses against her body and a desire not to be harmed more.
  • Warhammer from being used to build Eldia's infrastructure.
  • Cart from quickly carrying supplies for construction.
  • Colossal from her effortlessly crushing armies and conquering them.
  • Jaw from having her corpse eaten by her daughters.
  • Attack from her desire for freedom.
    • This one contradicts my first headcanon about Eren sending his own desire for freedom to past holders of the Attack Titan, but hey it's a headcanon, since they are not confirmed in the story I can accept all of them.

Eren's personality and obsession with freedom is result of him being conceived while Grisha held the Attack Titan.

  • Armin showing his book of the outside world to him just awakened the more Titanic side of Eren.
  • Plus Eren was able to see the future even before getting the Attack Titan.
    • This one also contradicts my first headcanon, but like I said, anything goes if not confirmed in universe and doesn't contradict the source material.

Children (and direct descendants within a certain amount of generations down the line) of Beast Titans take on some characteristics of whichever animal the Beast Titan they descend from were.

  • Example: if an Eldian was descended from an aquatic animal, they would have an easier time swimming, and possibly holding their breath underwater (if the aquatic animal was also an air breather like say a whale).
  • Mike Zacharias is descendant of a dog Beast Titan.

The ancient Eldians didn't stop at 9 Titans—at some point in ancient history, there were way more than 9 Titans.

  • Every time the power was split, the Titans grew weaker.
  • Some Shifters ate several of the other weaker Shifters throughout different points throughout ancient history in order to strengthen their own Titans, up until there only 9 Shifters were left.
  • Instead of split apart the power to more than 9 again, the ancient Eldians just chose to cap it off at 9 to prevent the Titans from becoming too weak.

MRS had 4 children each.

  • Maria's kids (eldest to youngest): whatever the name of the Northern district is, Shiganshina, Holst, and Quinta.
  • Rose's kids (eldest to youngest): Utopia, Trost, Karanes and Krolva
  • Sina's kids (eldest to youngest): Orvud, Ehrmich, Stohess, and Yarckel.

Reiner, Bertholdt, and Annie (RBA) initially believed that Eren was a distant relative of Zeke where a shared ancestor ended up on Paradis 100 years ago.

  • RBA also had no idea that Zeke's family were Eldian Restorationists or that his dad was named Grisha as Grisha was taken to Paradis before they were even born.
  • Reiner and Bertholdt found out that Zeke's dad was an Eldian Restorationist sometime between Clash of the Titans and return to Shiganshina, while Annie found out some time after the Rumbling.

After the Rumbling, the surname Jaeger disappeared literally overnight.

  • Zeke's and Eren's grandparents were trapped in Marleyan prison and died during the Rumbling.
  • Anyone else living in the outside world that had the surname Jaeger, instantly changed it for their own safety letting the people around them believe that their new surname was always their name.
  • While the surname went extinct, Jaeger did became a popular first name along with the name Eren on Paradis.

Paradis' destruction in the epilogue:

  • Tensions between the outside world and Paradis only worsened by Paradis being a fascist nation, with the majority supporting the Rumbling and hailing Eren as their martyr.
  • The outside world just bided their time until they eventually rebuilt technologically and took revenge for the Rumbling.

At the epilogue, the dog was the one who ended up getting powers, not the boy.

  • But not Titan powers as the dog wasn't in danger when entering the tree and didn't need an indestructible body to save itself.