headcanon/extra info.

[icy]

Physical Traits

When stood next to North or Pitch, Jack appears rather dwarfed, but when placed next to a normal child his height evens out to what you might expect of an 18-year-old. I place him at 5'10", tall for a Colonial but nothing outstanding by modern standards. His body itself is the reanimated corpse that drowned in Burgess and solely kept functioning by the grace/magic of the Man in the Moon (along with whatever hocus pocus he poked into Jack the night he was brought back as a spirit) relying on a blend of his soul (fun) and the cold essence of winter rather than anything directly tied to his former life. He can access memories and specific emotions from a golden tooth-casket, but they are specific to certain instances and won't spark off a flood of knowledge; Jack was never meant to become Jackson again, and he can't even if he wants to. It's akin to looking at an old photograph that brings back scents, sounds and vague pin-pricked thoughts, but never the whole story. (Case in point, that he saved his little sister but cannot recall her name or the face of his mother.) The casket is full of his baby teeth, so there are a handful of memories there for him to as of yet unlock.

With Colonial life having brought Jack up an undernourished shepherd with little need for actual strength, his limbs are whip-corded in muscle that served him well enough in life but now, with the abundance of food by new-age standards, he appears far too slender. His facial structure and height is all he had time to grow into.

Jack drowned as a result of cardiac arrest. Freshwater taken into the lungs is known to transfer through to the pulmonary system via osmosis, in this case acting as a freeway for the frost magic that was thrust into every inch of his veins. The dilution of his blood led to too much of it contusing under the softer skin around Jack's eyelids, darkening them with a sunken lividity that any medical practitioner, upon realizing he did in fact drown, would immediately find note-worthy (one of the only sure-fire signs that Jack was not immediately saved and left for at least several hours as night fell). The frost magic acts as a direct substitute for all his body's normal functions and when put in peril, he undergoes the early stages of death in small degrees. His facial muscles and neck begin to cramp with the onset of rigor mortis, a phantom ache that slowly peels through every muscle. The bruising around his eyes begins to transfer to the heavier sections of his body, purple discolouring his feet and ankles, nails darkening as well as any part of Jack that neglects to keep moving for very long. This occurs after extreme exposure to heat and one of the reasons he refuses to stay anywhere hot for more than a couple of weeks at most, prone to lethargy when warming up. With haemorrhaging having occurred while he drowned, if Jack gets too hot then his body begins to weaken just like the frost magic and he may cough up old gobbets long-since stuck in his lungs.

His blood is very much dead with only the frost magic giving him the appearance of blushing or paling by degrees, and his heart does not beat. Breathing comes habitually to keep his peace of mind, though he can cease at any moment and feel no ill effects. Jack can eat and drink, but it does nothing noteworthy to his overall frame and he needn't bother at all. His tastebuds are in full working order, although he inadvertently winds up chilling even a hot snack before getting halfway through it. He does, in fact, like to eat, and is unlikely to turn down sampling anything. If cut or injured, the frost magic knits him back together given time (a day or so, depending on the seriousness of the wound). His staff is directly linked to his power and channels it on a constant basis, yet he remains capable of producing his own ice and frost even without it. Flying becomes much harder, however, as he has always had it in-hand when doing so before and the lack of equilibrium throws him wildly off-balance.

Flight itself depends on the weather. If exposed to the gentle balmy breezes of the south or east, he can't go very far at all and will need to walk until he finds somewhere adequately cold enough to stir up a strong wind. In spring and especially summer, he will avoid countries where his frost melts inside half-an-hour and stick to colder regions.

The script describes Jack's attack on Pitch as lightning-based, which makes sense when old wives tales and ATLA, funnily enough referred to it as the Cold Fire back in way-back-when. He can summon it, along with sub-zero frost, whenever he wants now, but he largely prefers working with the simple icy talent nurtured and refined over centuries, only liable to break out the big guns if the threat is significant.

Mental Acuity

Three centuries of solitude have turned Jack into a carelessly over-invested person. Having never had to deal with anyone seeing or hearing him before, he has wandered through the world at his leisure and behaved exactly as he pleased as time taught him that if he didn't amuse himself, nobody else would. As a result, he sticks his nose in places it shouldn't go. Not as a defiant act of ill-manners, it simply fails to occur to him that other people will have something to say about his actions afterwards; he touches trinkets in rooms, ices this and that without a care, perches on furniture wherever he feels the most comfortable even if there is an army of comfortable seats free. When chastised, he can go either one of two ways; apologetic and self-deprecating, or deliberately antagonistic if he feels he himself is being criticized, not his behaviour.

Jack is old, for all that he appears suspended in youth. His misadventures with other people and lapses in judgement are not acts of real naivety (where he would need to truly believe in the good in everyone) and instead can be observed as fractures in social understanding. He's flippant and defensive when made to feel young or stupid, fueled by the resentment of someone who has never had any authority figure to look up to and had to be his own, setting his own moral code. Just as no one amuses Jack if he does not take the reins for his own sake, neither is anyone allowed to dictate his actions – even the Man in the Moon. Brought into the world as a spirit with an 18-year-old's cleverness, he aged internally with the long years and brewed an inner sagacity that is tamped down on by his Center. When angered, Jack doesn't hold this back. He's sarcastic, bitter, vengeful: this is the Spirit of Fun, not Happiness. Fun can be whatever makes Jack feel better.

“Snowballs and fun-times” don't eclipse the true extent of his Center. He can be brash and ever so slightly mean (flinging a young boy down a road on a causeway of ice definitely qualifies) but never cruel, and he knows his limits well (safely depositing him in a bank of soft snow). When around others, his natural inclination is to put the welfare of children above that of adults, not above suggesting that grown-ups should withstand nightmares instead of children.

If insulted or mocked, he isn't a Peter Pan figure to fly off in offense shaking a fist. Jack can be bitchy and crass, only pushed to such an extreme if he knows children aren't around, the kind of person to cover a driveway in black ice and laugh as someone who hurt his feelings falls on their backside. If he isn't protecting the little ones, he'll more than protect himself. At the other end of the spectrum, he loves to be loved and pledges all of himself to those who give welcome. As a friend he would stand by someone's side even if they were in the wrong and defend them without a care for how it made him appear. There's nothing so important as keeping those who love you safe, this is ingrained and the most stubborn of his beliefs that was reinforced when he witnessed his First Memory.

Romance

Wasn't and isn't a major factor, in short. Having had to learn about the birds and the bees by watching couples have sex (usually from a distance, chagrined enough despite his invisibility owing to what they were doing) it became very apparent that he was far too cold to enjoy any such liberties. He can only keep people cold, and when he finally met other spirits that buoyed his mischievous reputation, the ones that found him comely enough to kiss or embrace never did so for very long. As such, not wanting to hurt anyone with his curiosity, he remains a resigned virgin.

Love is for people who can be together forever. Jack is unable to offer that to a mortal, even if he adores them, so he smothers any romantic inclinations out of the good of his heart and keeps his suffering on an internal level as he lightens their own.

Random Facts

His full name is Jackson Overland Frost. Before the Man in the Moon chopped out the middle chunk of his name and pulled him out of the pond, there was no 'Jack Frost' to speak of, only the old tales dreamed up by Vikings and everyone else since. He was shoehorned into an open role and when he found out that people knew his name, assumed for a long time that he needed to do something to live up to their expectations. Embellishing on the fables came to him easily though no one ever saw him or believed he truly existed, and he kept the old myth alive out of a vague sense that it was one of the things Manny would have wanted him to do. (It also filled up a lot of his time.)

Over the years, Jack has changed shirts several times according to fashion. Keeping his original outfit for a hundred years or so, he changed the raggedy old cloak for a simple coat that lasted him until he happened on his hoodie in the 1980's. It happens to be darted for a girl, and was the only one that didn't swamp him after he got it into his head that the design looked particularly cool, wanting one for himself.

His favourite thing to do is fly.

Salt tastes awful to him (as an ice-based spirit) and he prefers sweetmeats and candies when he does eat, not above slicing himself a strip of apple pie off a window and zooming away to enjoy it without a by-your-leave.

Jack is an accomplished reader and writer. Growing up from the start with the bright mind of a young man and learning throughout his would-be natural years up to around 70/80, the age he lived in did not cater to those who found it difficult to do either, forcing himself in quiet moments of solitude to borrow books, slate and chalk to practice his skill-set which inevitably wound up at a more than acceptable level. Knowledge is something he craves. The Man in the Moon never gave him anything, never showed him how to be Jack Frost the Winter Spirit as he supposed he must have designed, so with time Jack's curiosity has matured into highly self-reliant resourcefulness. His handwriting is, however, a scrawling mess because he has little enough patience to refine it.

Mathematics and sciences are his obvious weak spot, academically. Too much time needed to pore over boring details is needed and, unlike with reading and writing which has always proved useful, these subjects do little but make him feel sleepy.

He loves to hear fables and fairy tales about himself, generally because there are so few.

He hated the 70s because everyone thought he was best friends with the Groundhog, who wouldn't shut up about a stupid stop-animation movie.

When traversing battlefields of wars conducted in winter, he covers the faces of the dead with a blanket of frost.

Every pond and lake he has ever frozen has been done so to a thickness that doesn't break all winter.