Because it had to be done!

So Jack had been around for a very long time and during that time he had noticed some very odd things. One of these things was a blue box that would show up in seemingly random places. From this box would come a man, usually oddly dressed but always carrying the same air of authority and knowledge about him. This man would often look right at Jack when he was nearby, but never more than that, and it was always short lived. As if he knew something was there but was ignoring it. This began to grate on Jack's nerves until one day he found the blue box and the man, even if he looked Different Jack was certain it was the same man, sitting outside, alone. Jack grinned as he gathered snow in his palm and readied to throw it and see what sort of reaction he got.

"I wouldn't do that if I were you young man."

Jack pouts but lets the snowball drop before perching on his staff and watching the strange man curiously.

"You can see me?"

"Of course I can see you, I have seen you many times flitting around."

Jack pouts at the response.

"Then why haven't you said anything before."

"Because no one else can see you and it is not my place to make believers of them. You need to do that sort of thing on your own."

Jack's pout deepens and he sticks out his lower lip to show his displeasure.

"So why talk to me now?"

"No one else is around, my last companion had to go home just before my trip here and so I do not even have those extra ears listening in."

"Oh." Jack studies the box for a moment, the strange man watching him as he does. "So what is this thing? It's strange."

The man chuckles. "This is the T.A.R.D.I.S. It allows me to travel through time and space."

Jack blinks, he had never heard of anything like that before.

"Are you some kind of witch then?"

The man laughs heartily at the question, but soon is able to answer. "No, no nothing like that. I'm The Doctor. I would take you with me on a trip but I'm afraid it would mess with a few things if I removed you even for a short time."

"Oh." Jack seems to droop a bit on his perch. "So how come you're not always the same then? I've seen you with many different faces, some I've seen before but there are always a few new ones now and then."

"Ah, that is because of my... regeneration. It's a type of shape-shifting."

"Really, that sounds fun."

"I suppose it can be."

For the next several hours the Doctor and Jack shared stories of their lives. The Doctor told Jack how he was the last of his people, not sharing any details of how or why. And Jack told his story of waking up and knowing nothing but his name. The Doctor had frowned slightly at this information but covered it quickly before Jack could ask.

When it came time for the Doctor to leave he bid goodbye to his part time companion before stepping into his machine and disappearing in a buzz of whirling sound.

Jack never forgot the kind Doctor or his stories, it kept him company through the long lonely nights and he would keep his eyes open for that strange blue box. Years of this game of hide and seek and Jack learned that the Doctor must not like Christmas very much because he was always causing trouble during it. Jack didn't mind though, it was entertaining to watch as the Doctor and his many companions got themselves into and out of trouble, occasionally he would even help out, when he could.

Then Jack had been made a Guardian, the Guardian of Fun. He was happy he finally had a family and the answers to why he was there and who he had been. He understood exactly who he was and what he was meant for. Children were beginning to believe in him now and he felt overjoyed at the sensation of touch and the novelty of a conversation.

It was this last one that lead to Jack seeking out North to learn more about his fellow Guardians.

"Alright, so can you tell me about Bunny now? You've told me about Sandy and Tooth, but I want to know about Bunny."

North gives a chuckle as he settles in. "Yes, yes, settle down Jack. Hmm, where to begin? Ah, well for starters Bunny is last of kind. The Pooka were once well known throughout the universe for their mastery of machines and were even rumored to be able to travel through time and space at will. Also they are shape-shifters, very tricky and cunning."

Jack furrows his brow and interrupts North. "And he doesn't like Christmas much either, does he?"

"Bah, he feels Easter is better holiday, but you and I both know he is wrong, da?"

"Uh right." Jack gets up and floats nervously beside his staff. "Um, I've gotta go, things to do, snow days to deliver. Bye North."

And before North can respond Jack is flying out of the workshop and taking off into the sky. His mind was whirling nonstop as things fell into place and before long he found himself outside of the Warren. Quietly he sneaks inside and begins his search, because he knows it has to be there. It just has to be, because it is the only place it can be. Then, back in the very furthest reaches of the Warren Jack spots an oddly blue box hidden away behind flowers and trees and boulders. Moving closer and there it is that one man's strange box, only it looks older and more beat up than he remembers it being. Just as he is reaching out to touch it he is stopped.

"Oi, Snowflake, what to ya think yer doin'?"

Jack turns and looks guiltily at Bunny, drawing back his hand from the box.

"I just, I was curious. North was telling me about you and, and it all sounded like I had heard it before so I had to make sure"

Bunny glances at the box then back to Jack with a sigh.

"Ye're darn lucky I like you kid. Come on, let me fill you in on things. Been a while since our last sit down. Longer for me I suspect."

"Oh... Is that how it all works then? The time traveling stuff?"

"Yeah, but the T.A.R.D.I.S. hasn't worked in centuries, I dismantled it myself when I took on this form."

"Why?"

"Found a purpose, a home. Didn't have a need for it anymore."

So Jack followed along to learn of the one time Doctor and the for now Easter Bunny.

What clinched it for me was realizing they both shape-shift. Spread the word!