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ANOTHER Ninjago head canon that live by is during the older seasons Jay would try to keep his hair kept and neat but the more he used his elemental powers the more staticky it would get making it more fluffier (idk how hair works but just work with me here) and after every mission he’d fix it. Eventually he just gave up trying to keep it neat and it became the way it is in the newer seasons
I know a lot of people are saying that Kai and Nya had a babysitter and whatever, but guess what.. who cares? Allow me to explain:
A Babysitter is someone who comes for a short amount of time to take care of kids. A babysitter needs money. This ‘babysitter’ definitely had her own family and I don’t think a random stranger or even if the babysitter was a good neighbor would raise someone else’s kids and provide for them and support them and love them for free. She most likely came in only to feed them, and left. Or left the minute Kai turned ten. Maybe she gave up when no more money was coming her way, and she only came to feed them for a year and that’s it. We don’t even have enough information to conclude any of this, especially not if she was a good, loving babysitter, which she was likely not. Because if she was, Kai and Nya would be mentally healthier.
When kids are growing, they look up to their parents, because they are emotionally connected with them. Kids mimic emotions from their parents, and look up at them for validation of their own. Nya was really young when Maya and Ray were captured. Kai was very young too, but old enough to know what love is because he most likely remembered his parents loving him. Now on the other hand Nya probably had little to no memory recall of her parents at all, much less the idea of what ‘love’ is.
When Maya and Ray were captured Kai was the only person left who Nya was emotionally connected with. Kai was the only person who could fill the role of being a loving person in her life, someone she could relay on and trust with vulnerability. I don’t think some children would just suddenly trust a random adult in their life, especially not Kai (remember how hesitant and suspicious he was when he first saw Wu). 
If this babysitter was that awesome, dependable, or trustworthy, Kai would not have trust issues, Nya would not need to feel independent, etc etc. Again, Both siblings would have a little more healthier mindsets.
Kai, as a child, loved Nya since the beginning. When Maya and Ray disappeared, he did raise her. You could interpret this sentence in many ways- raised her by love, raised her emotionally, raised her by providing for them both, raised her by protecting her. I strongly believe in every one of these and more, but this furthers on to my point: babysitter or no babysitter, at the end of the day, Kai did raise Nya. And I think for a small child who was just as lost and scared, he did his very best.
A child forms their idea of love normally by looking at their parents relationship, and by observing how parents treat them. Kai had a slight foundation in this already, since he loved Nya since the beginning. Nya however, as I mentioned before, likely had little to no memories of her parents. So, everything Nya learned about love, how to love, etc was from Kai. And with this, Nya had understood and developed her own love languages, and proceeded to use what she learned from Kai and reciprocate it. This was undoubtedly Kai’s biggest mental support during his childhood. And with what she learned from Kai, she started to also love Jay.
AND I AGREE?? WE HAVE THE SAME THOUGHT PROCESS I LOVE YOU VERY MUCH MITZLE
and again, adding to all of this, it’s also sometimes easy to forget that ninjago is a kids show- which is exactly what angers me more. Kids should be shown romantic relationships are important; there is nothing wrong with that. However hundreds of kids could relate to a sibling relationship, and could maybe even learn from Kai and Nya, and get closer to their own siblings! When I was younger I looked up to Kai, because he was an older sibling and I could relate to that. Other kids could do the exact same!
The writers have indeed diminished the value of Kai and Nya’s relationship, overlooking it and portraying to so many kids that romance reigns over family every time. I just wish they would change, because Kai and Nya are siblings and downgrading the important value of sibling relationships seems to be the writers ultimate goal. And honestly? This really needs to stop.
Respectfully, some of you in the ninjago fandom REALLY need to get this in your ears:
the amount of grief jay felt about nya’s death IS NOT LARGER THAN THE AMOUNT OF GRIEF KAI FELT.
familial love and romantic love are two different things. and yes, depending on circumstances and the people themselves, one can be stronger than the other.
BUT NOT IN NYA’S CASE. KAI AND JAY LOVE NYA EQUALLY. JAY DID NOT MISS NYA MORE THAN KAI. KAI JUST HID HIS GRIEF, AND MAYBE IS COPING IN A DIFFERENT WAY. KAI AND JAY ARE DIFFERENT PEOPLE. BUT THEY LOVE NYA EQUALLY.
so stop saying jay was more upset over nya’s death when kai literally held her when she was a child and raised her and was there for nya her entire life. nya missed them both, and they both missed her. thats it.
The problem i always had with people saying Lloyd is 23 or something in dragons rising BUT mentally he's like 18
Or in Controversallized, he's 18 but mentally 16 or whatever,
Is that MENTAL AGE IS NOT LINEAR GUYS
I feel like people miss this and maturity as a concept.
Longer rant below
It was true at the beginning when he got aged up that he was ~8-10mentally and ~14physically, and for a while it was linear maybe, but mental age is more complex than a thing that follows your birthdays, take examples from real life.
A child under pressure, responsibility and a role they have to be forced to fill, with the addition of trauma will mature differently and faster.
Just like when a kid is stripped away from their family in real life, maybe due to war, abuse or financial reasons, the kid must learn the skills of older ages to manipulate their sourroundings to help them survive. That's forced maturity and a childhood lost.
People could be well in their 30s and have an 18yo more mature than them, its all about the conditions of growing up, and what hardships they had to adapt to.
Also, think about this: What does it even mean to be a specific age mentally? How does a mentally 23 yo differ from a mentally 18 yo person? Its very relative...
We can maybe see Lloyd act more unmature and childish than the others in pre oni trilogy seasons, but ultimately always trying to seem wiser than he actually was because then it was true that he got aged up, and his mental age didn't follow up for a while, but still maturity was expected of him. However i feel like that gradually fades away as we go further, and i firmly believe that his mental age has caught up to his physical a long time ago.
Even if tomorrow's tea never happened, he'd be more mature than his age due to the experiences he's lived through.
Also, mental age is NOT linear to behavioural skills.
The tomorrow's tea left effects on his social skills and behaviour, only because in addition to a fucked up early childhood, he literally skipped the late childhood development stages, arguably the most important one for learning social cues and learning to build connections, in addition to immediately being put into a situation of great responsibility, forcing him to learn all the skipped skills afterwards. And this arguably wasn't because he got aged up, it was the events he got put into. We can also see this in real life with people who were forced to grow up too fast.
If you were to make conversation with an adult who lacks certain aspects of social skills due to reasons, you wouldn't say they are unmature. You'd probably think they are maybe autistic, but not unmature.
And developmental holes are probably the source of many of his issues later on, like trust issues (on both ends, (w Pythor, Harumi, Akita, Garmadon post res), the inability to properly express empathy (DR s3pt1 when reacting to Arin's parent's death), or isolation in crisis (DR, Controversallized, Oni trilogy, Splinter in the Blind Man's Eye,...), and many others.
But these are NOT tied to maturity.
It's simply the effects (and mental health problems) due to one's development.
I'm not gonna go into the psychological aspect of the opposite, when people return to their childhood preferences/behavioural patterns after adulthood because they miss what they didn't have, because that is a different topic.
That being said people can still act younger in times, but thats normal, even healthy, and i'm all for preserving youthfullness. Heck i literally work in a club/bar but will play minecraft and build ninjago sets afterwards. If i see a cool bug i will pick it up and show it around, but that doesn't mean i won't be reliable at work or solve that differential equation for uni projects. Maturity is also the ability to act according to situation.
So... Now that i diverged this much
I don't believe that, and at the very least in dragons rising, that his mental age would be younger than his actual physical self. I believe after all the ninja went through, they long are all more mature than what an average person would be at their age.
And i hope to see that more highlighted in DR with Sora and Arin, (maybe even Wyfy). Sora was forced to mature a bit more than Arin was growing up, and that is apparent among them, with Arin acting like a typical ~15yo, while sora acts more young adult like. But I'm sure the pre ninja Arin and the Arin we'll get after s3 will be very different. Not because the passing of time, but the mental maturity he gained due to experiences (not necessarily positive ones).
But change my mind i guess
Welp, thx for reading my ramble, here is a potato
I'm so tired of people implying Nya's character is dependent on Jay's, when literally every single Jay arc revolves around Nya. Like have we even watched the same show?
Jay's true potential? Being himself around Nya. Jay's fight with Cole? Only because Nya suddenly has a thing for Cole. Skybound? Do I even need to say it? Prime Empire? Losing Nya is what motivates him during the final level because Jay can apparently only shine on his own when all the other ninja are eliminated in some way and he's the last one standing. His whole personality in the movie is shy and awkward with a crush on Nya.
Meanwhile Nya built a name for herself as Samurai X when she was a young teen because she was tired of being overlooked and stuck in her brother's shadow. Her interest in Cole might have been a little forced, but at least it proves she's open to alternatives, Jay is not. Possession is Nya being a perfectionist and embracing her flaws and overcoming the fear of failure in order to unlock her true potential and become the Water Ninja. Skybound is Nya trying to find her place in the team and dealing with gross misogyny. Hands of Times is Nya passing down her samurai armor. In Hunted her mission is to protect Lloyd and keep their hope alive. Seabound is about Nya's mommy issues, going with the flow, accepting the ups and downs of life and the importance of self sacrifice. Jay is only one of the people she sacrifices herself for. Then that one floating lantern message from one of the citizens of Ninjago: I'm suRe JAy mISsEs yOU a loT. Yeah, right. Jay and only Jay. Because Nya is all about Jay in their heads just like some of the fans apparently. Movie Nya is a badass motorbiker who looks up to the Lady Iron Dragon and doesn't even acknowledge Jay.
Not to throw shade on any Jay fans, I just wanted to point out how Nya is normally the more independent of the two, has more character development and protagonist energy. I'm so tired of her character being reduced to being Jay's girlfriend, Kai's little sister or heck even Lloyd's older sister, and I'm one of the biggest dragon siblings fan there is. Nya deserves better, so much better than this.