This shows that he deeply cares for children even though they may never see or hear him and highlights why he is a Guardian. Due to his years of isolation, Jack seems to be taken off-guard by shows of affection. An example of this was when Jamie hugged him. Jack was so caught off-guard that he didn't even respond for a moment but then warmly returned Jamie's hug. He was also surprised by Tooth hugging of him after he officially became a Guardian but didn't seem to mind it. Before Jack Frost became an immortal being who possessed the power over ice and snow, Jack was once a teenage human boy who had a family of his own years before the current timeline.
Like his current form, Jack was mischievous, liked to have fun and play tricks on his friends and his younger sister. When Jack and his sister got themselves in trouble while they were ice skating on thin ice, Jack made up a game of Hopscotch, and using his staff, Jack saved his sister from the cracking ice, at the cost of his own life. When Jack Frost was reborn he lost all memory of his previous life and immediately began his adventures of fun and mischief, discovering his powers.
The Man in the Moon only ever told him his name, and he quickly discovers no one can see him when he enters a village and is walked through for the first time.
The story continues with Jack causing mischief in St. Petersburg, Russia. Noticing it was a fun day, he calls the wind to take him back home, to Burgess.
As he arrives at Burgess, he decides to give it a snow day. While Jack is having fun, he accidentally knocks a book out of the hands of a child named Jamie with his wind. Jack finds the book interesting and asks Jamie about it, but Jack knows that he can't be seen or heard by Jamie. Just then Jamie's friends, Caleb and Claude , rushed to Jamie and tells him about them having a snow day and Jamie asked them if they were going egg hunting on Sunday.
Jack followed Jamie to his house listening to their conversation. When the boys bring the Easter Bunny in to the conversation Jack joined, saying that Bunnymund is real annoying and full of himself. When Jamie's mom comes out of the house to give Jamie his winter hat; she brings "Jack Frost" to the conversation by saying: "Careful! You don't want Jack Frost nipping at your nose! Jack takes that offense and decides to have a little fun with Jamie, so Jack throws a magic snowball that hits Jamie in the back of his head causing a snowball fight between him and his friends.
When Pippa accidentally hits Cupcake , and everyone gets afraid. Jack, wanting to continue with the fun, hits her with a snowball, changing her attitude from mad to happy in which starts a game of chasing. The ground was slippery causing Jamie to fall in his sled and skate to the street, so Jack makes an ice path around the street and helps Jamie return to the park where Jamie flies so high that he goes over the statue of Thaddeus Burgess and gets hit by a sofa. Jamie, excited, reveals that he lost a tooth causing the conversation to change to the Tooth Fairy. Jack tried to remind them about the fun they just had, but his beckoning turns to sadness when Jamie walks through him.
Jack is later spying on Jamie that night when he tells his family about the fun adventure he had and the new drawing he made.
He also tells them about the tooth and planning on seeing the Tooth Fairy. Jack then leaves and asks the Man in the Moon what can he do to be seen by someone as he has tried everything. Just then the Sandman's Dreamsand arrive. Jack intercepts the Dreamsand causing it to change to the shape of a dolphin. Just then a shadow passes him. Jack, curious, follows it to an alley revealing to be Bunnymund. At the North Pole, Jack meets up with the Guardians and they reveal that Jack was chosen by the Man in the Moon to become the next Guardian and that Pitch has returned.
Jack turns down the offer as he doesn't want to be someone who's stuck somewhere, finding ways to bribe kids. Tooth tries to explain what they do and the joy they bring to kids, but Bunnymund thinks Jack doesn't know anything about bringing joy to children causing a fuss between him and Jack. North takes Jack away and explains to him about The Man in The Moon must have known that Jack has something special in him and North reveals his center, which is Wonder, through the use of a nesting doll of him.
Jack, still confused, doesn't know what his center could be. Just then Bunnymund reveals there's trouble in Tooth's Palace and they have to make their way to help Tooth. On their way there, it's revealed that Pitch has sent his Nightmares to catch all the fairies and collect the teeth of the children of the world. Jack saves Baby Tooth from one of the Nightmares before they arrive inside of the Palace to find a panicking Tooth. Pitch then confronted the Guardians and after a battle between then he escapes. Jack, curious, asks why Pitch took the teeth and Tooth reveals that the teeth hold the greatest childhood memories, the reason why she collects the teeth.
She also reveals that the Guardians were all somebody before they were chosen by the Man in the Moon, even Jack. Jack, surprised, asks her about his past life and about his family to which Tooth asks if he really doesn't remember anything and that she can't help him since Pitch has his tooth box. North plans to collect the teeth to keep the children believing in Tooth.
North asked Jack to help them collect the teeth and in return they would help him get his memories back and Jack agrees to help them. The Guardians go around the world collecting teeth and making a competition of it. Abby starts growling at Bunnymund and Jamie tries to stop her. Jack wanting to have fun with Bunnymund, makes the alarm go off, causing Abby to attack Bunnymund and make him jump around the room. Jamie flies out of bed when North lands on it and Sandy catches him. Sandman puts Jamie to sleep and then goes to fight Pitch's Nightmares that have appeared with the help of Jack.
Jack is confronted by Pitch until Sandman joined him and slammed Pitch against a few building, with Jack commenting on not getting on the Sandman's bad side. Pitch pretends to be afraid of the two until he reveals his Nightmares. Soon Jack and Sandy are in the sky battling the Nightmares, but the Sandman is surrounded and soon Pitch attacks him, turning him into more nightmare sand. Jack used a powerful wave of ice which destroys the nightmares, but he started to fall from the sky until he was rescued by Tooth.
Back at the North Pole, the Guardians make a memorial for the Sandman. The Guardians decide to work hard for Easter so they could keep the children's belief in the Guardians.
After the eggs were ready, Sophie fell asleep and Jack decides to bring her home. After Jack was able to put her on her bed, Jack heard a voice calling him. The voice led him to Pitch's lair where he found the kidnapped fairies and was confronted by the Nightmare King himself.
Pitch tempted Jack with his memories and taunted him with his fears of not being believed in, keeping Jack distracted long enough for his Nightmares to destroy Easter. Once this was complete, Pitch finally gave Jack his Tooth Box before disappearing.
Jack saw the children stop believing in Bunnymund and found the Guardians disappointed. They told him that the Nightmares attack the Warren and the eggs didn't survive the confrontation. Jack made his way to Antarctica so he couldn't mess up again, but was confronted by Pitch, who wanted to recruit him. When Jack refused, Pitch revealed he had Baby Tooth and told him he will give her back if he gave him his staff. Jack agreed, but Pitch tricked him. Baby Tooth pecked Pitch's thumb, making him threw her away while he broke Jack's staff afterward.
Pitch attacked Jack with nightmare sand which slammed him against an iceberg making him fall into a crevice. Jack found Baby Tooth and felt sad that he kept making mistakes. Soon after Jack's memories called him again, making him remember that he still has his Tooth Box. The flashbacks showed Jack some of the fun memories he did have with his sister and also showed him the moment when he saved her from the ice.
These memories made Jack realize that he always has been a Guardian and gave him the courage to fix his mistake and save the Guardians and the children of Earth from Pitch. Jack was able to fix his staff and made his way back to Pitch's lair to rescue the fairies, but found out that they couldn't fly since there were only a few lights left. Jack noticed that the last light was Jamie and he made his way back to Burgess to recruit Jamie. Jamie seems to start losing hope in the Guardians until Jack makes an egg with his ice powers in his window.
Getting Jamie's attention, Jack makes a bunny and makes it come to life and jump around the room.
Jamie asked "Jack Frost? When Jamie revealed he can see and hear him, Jack gets excited about having his first believer. When they hear North's sleigh, both of them rush outside.
Jamie reveals that he can see Jack and the other Guardians. Bunnymund thanks Jack for making Jamie keep his belief in him. When Pitch appears, Jack goes to fight him, causing the other Guardians to lead Jamie away. Pitch being more powerful than before beats Jack and makes him fall to the alley where the others were.
Pitch approaches them but was hit by a snowball by Jack. Distracted, they escaped and went to gather up Jamie's friends. With the help from the other Guardians, Jamie's friends start to believe again. Pitch asks them who was going to protect the Guardians if the Guardians were protecting them. Jack reassured Jamie to not be scared since the Nightmares are just bad dreams and Jamie volunteered to protect the Guardians causing his friends to join him.
Pitch then sends a wave of nightmare sand their way but once Jamie says, "I do believe in you. I'm just not afraid of you!