Well, as Nick would say, I'd forget my head if it wasn't attached to my neck. My deepest apologies to everyone for taking so long to get to this, but here - at long last - are the answers to the Easter Egg hunt in this story. Enjoy!
Chapter One
This wasn't really listed as an Easter Egg, but the Sisters Six - as pretty much everyone guessed - are a nod to the Sinister Six present in most incarnations of the Spider-Man storyline. Spidey's counterpart in the world of Zootopia could be Spider-Ham (a pig-based bit of self-parody by Marvel), or Spider-Fox (Cimar of Turalis WildeHopps can explain that one, having done a fanfic based on a fan comic of the idea). Take your pick, but I doubt either would be complete without some version of the Sinister Six.
Chapter Two
"It was hardly unheard of for Judy's 'May have a problem" to equal someone else's, 'the living room rug is on fire.'" This is a nod to one of Marty's lines in Back to the Future.
"Nick suppressed the urge to ask if they had a duplicator box in the house." This is a reference to a bit from the Calvin and Hobbes collection, Scientific Progress Goes Boink - the same bit, in fact, that gave me the idea for the trick it involves.
"Run for it, Marcie!" I was thinking of the line "Run for it, Marty!" from Back to the Future, though I suspect that this was a little too subtle since no one got it.
The name "Runo," also used in the Sisters' Six stunt, was borrowed from a Bakugan character - who, if she had appeared in the Zootopia universe, could very easily have been Judy's sister.
Cinder/Cindy is a nod to Cynder from The Legend of Spyro.
Jordy's superhero costume and method of attack are based on the Pokemon called Electabuzz. I thought it would be fun if Zootopia's pop culture (movies and such) had certain Pokemon in humanoid form as superheroes.
Sisters Six has already been explained.
Funnily enough, I can't find the Magic Schoolbus reference here.
Chapter Three
"We start relaxing them (the rules), and then it's nothing but work, work, work." This is a nod to a line from Wesley/The Dread Pirate Roberts in The Princess Bride.
The show Jordy mentions involving polymorphs is a reference to the series Lost Tapes, specifically the episode Werewolf. Do not watch if you have an aversion to blood or have an overactive imagination.
'Judy was outraged. So was the doe in charge. "That did it. Who did that?!" This line was borrowed from a scene in Balto where Boris, like Nick, was flattened by a snowball out of the blue.
"I am warning you... you're messing with an old pro." USA Patriot nailed the Ben 10 reference, when Nick quotes the line Grandpa Max used in the Christmas episode just after he too was pegged with a snowball.
The line about 'Christmas songs, familiar and slow' is paraphrased from a Calvin and Hobbes Christmas poem (I forget the title).
Nick's second-to-last line in the chapter is a reference to Lilo and Stitch
"Nick had left the door ajar, knowing that one should never shut themselves up in a closet." Kudos to Kyla/RogueActive for spotting one I forgot to mention. Yes, this is a nod to The Lion, the Witch, and the Wardrobe by C.S. Lewis - and basic common sense. Getting stuck in a wardrobe isn't fun, believe me.
Chapter Four
I have no list of Easter Eggs for Chapter Four, although I could mention here that Marian Wilde (yes, as in Maid Marian) is loosely based on Aunt May as seen in the Spider-Man trilogy and Spectacular Spider-Man. With the way my brain works, though, I probably slipped some in there without even thinking about it. Good luck.
Well, that's it for Christmas in Bunnyburrow. My thanks to everyone who read this story, and I hope you'll check out my other works as well. Zootopia has given me a number of ideas, so it looks as if I'll be cranking out stories for a long time to come.
As an added bonus, here's a heads-up: I have been working for some time now on a series of fantasy novels (the first is being looked at now), some of which involve anthros. It's not quite Zootopia, but if I can sort out the copyright concerns I hope to tack teasers from my anthro stories onto the ends of my future Zootopia fanfics. So stay tuned!