He needed someone to love, to care for, to see him. The fates saw fit to give him a baby Pooka. Jack didn't intend to be a father, it just ended up working out that way.
It can be read here
This Fanfiction contains examples of:
- Adult Fear: Pitch grabs Desmond. And later the kid is with the Guardians while they and other children are surrounded by Pitch's forces. Regardless of how much faith you have in the Guardians, that had to be horrifying for Jack.
- Blood Knight: Bunny showed some tendencies towards this in chapter 9..Then he gave himself over to the joy of the fight.
- Deadpan Snarker: Jack. And Desmond has obviously picked up some of his papa's mannerisms.
- Everything Trying to Kill You: Australia. Lampshaded by Desmond."So, in this country, everything is trying to kill you? Even the grass?"
- Gosh Dang It to Heck!: Jack practices this. Justified given he has an impressionable child to care for.
- Hates Being Touched: Jack flinches when North reaches out to touch him. Given he has no problem with Des, it's likely that those he knows well are exceptions.
- Interspecies Adoption: A baby Pooka is raised by a human. Well, dead human turned spirit.
- Interspecies Romance : According to Word of God, this will come up.
- It has been lampshaded by Pitch when he saw Desmond and believed Jack and Bunny had had a kid together.
- Let Us Never Speak of This Again:Bunny: They don't mention the sword-swinging fox.. Ever.
- Like an Old Married Couple: Jack and Bunny.
- Noodle Incident: Desmond once gave everyone haircuts. And locked the Snow Queen's brownies in the kitchen. And tried to eat the Ice Palace once.
- Parental Abandonment: Desmonds parents. But mommy and daddy had a good reason for abandoning him. Namely that they wanted him to live and not die with them.
- Parental Substitute/Promotion to Parent: Jack. Although he did try to find someone else to do it because he didnt think he could.
- Shell-Shocked Veteran: Bunny in Chapter 12. He winds up in an Angst Coma for a bit.
- Sink-or-Swim Fatherhood: Jack was hit with this in the first chapter.
- Stunned Silence: When Jack reveals his status as a single parent.
- Tempting Fate: For all his years, you'd think Bunny would know better.Bunny: "Jack probably wouldn't notice a thing."
- Voluntary Shapeshifting: Desmond pulls this off to look like his papa.
- Wham Line: "[Pitch] claimed to have killed your child. He lied."
- What the Hell, Hero?: Jack calls out the Guardians on their lack of interaction with kids. Although he does acknowledge that Bunny watches the egg hunts. He also calls out Manny for ignoring him for three hundred years then expecting Jack to just be a Guardian on his say so