After sending up every manner of holiday institution over the past decade, it was time for “Robot Chicken” to break its annual Christmas Special out of the usual shell: Rather than the familiar collection of fast-and-furious animated sketches, this year there's a single epic storyline. At least, as epic as the Nerd's search for his biological father at Christmastime can be.

Tom Root, executive producer and co-creator of the Adult Swim series, and writer/director Tom Sheppard share with SPINOFF their path to the holiday tale, why it didn't end up including a particularly intimate elfin denouement, and whether the resurgence of "Star Wars" means there's more skewering of the franchise ahead.

Spinoff Online: I imagine it's just super-easy to sit down every year and say, "OK, we've got another Christmas special to do. Tons of ideas!" How did you zero in on what you wanted to do this time around?

Tom Root: Well, I think because we've done it so many times, everyone from the network on down was open to us shaking it up and doing something different, and so the idea came about, I think from the get-go, that we just wanted to tell one continuous story this year. So, it's one of the few times we've abandoned the channel-flip format, and we're just telling a complete story from start to finish.

Tell me about what that did to the creative process, and the fun that you guys have along the way.

Root: Well, in the writers room, we got pretty cranky, because we really like our system where we browse the Internet until about 2 p.m. and then start cranking out half-baked ideas. And as soon as we had the story, we actually had to become like a real writers room and collaborate and come up with an outline and follow the outline. We did not like that at all. [Laughs] But I think the result was – the experiment was a success, I would say.

Who had the "Eureka!" moment, as far as the storyline goes?

Root: It was long enough now that I don't remember. I think we all kind of agreed upfront that the Robot Chicken Nerd character was the only character who could sustain a full-length story. We have a lot of characters who are recognizable – like the Humping Robot – who you would never want to watch a full quarter-hour with. So it was either going to be the Nerd or Bitch Pudding, and she has just had her own special. So, we knew it was going to be the Nerd, pretty early on. And I don't remember. I think the rest of it is – the Nerd going to the North Pole and meeting Santa Claus, I'm sure, was about 30 seconds after we decided it was going to be about the Nerd, because it just seemed like the most obvious story to tell with him.

You also got to load this up with a lot of fun allusions to offbeat Christmas-y tie-ins. I think the first joke I've ever seen with Fred Claus – including when I saw "Fred Claus" – so tell me what was the fun of what you wanted to pay homage to in this one, picking and choosing the little references and things you could sneak in.

Root: We didn't really think, well, it'll be nonstop parodies of things. But every time we had a story obstacle to conquer, like, "How is he going to get up to the North Pole?" there kind of is a Christmas-y answer to that question. Like, "The Polar Express goes to the North Pole. What if he jumped on the Polar Express? Who would he meet on the Polar Express? Who's a character that was fun on a train, other than Danny DeVito in "Throw Momma From the Train"? Sure: John Candy from "Planes, Trains & Automobiles.’” And, "Hey, 'Snowpiercer' had snow and a train." What I'm getting at is that we didn't work too hard. [Laughs]

Tell me a little bit about what I'm sure is always fun every time out for you guys: the casting and who's going to play who. Who you want to reach out to? Who in the stable gets to hold their hand up for certain characters?

Root: Well, the one thing I just want to mention is Seth [Green] does an amazing Vince Vaughn. So, there was never any doubt. He wasn't going to let anybody else play Fred Claus. [To Sheppard] Who else do we have in this one?

Tom Sheppard: Oh, God …

Root: We should have come in with a list.

Sheppard: Well, we'll have to get back to you on that, because I can't remember who played Chris Evans from "Snowpiercer."

Root: Well, I can say that we're always happy when we can bring back the Nerd's parents with –

Sheppard: Michaela Watkins and Henry Winkler. They're just –

Root: Michaela's one of our all-time favorites. We would use her in everything if we could. She's just so funny and that voice she does for the Nerd's mom kills us. And Henry Winkler is like the perfect choice as the Nerd's father, and of course, we love having him in as much as possible. Since we're just a small cable show, we don't have a ton of latitude about how many people we bring in and so pretty quickly we started filling up spots with who was going to be necessary. I'm trying to think. [To Sheppard] Did we have any stunt casting?

Sheppard: Not really. No.

Tell me about – aside from doing a killer Vince Vaughn – Seth's role in this one, in general. What was his creative contribution to this particular installment, both as the voice of the Nerd and as a producer?

Root: Well, because he plays the Nerd, he's real particular about how the Nerd sees the world and how he reacts to the world. There's not a mean bone in the Nerd's body, which is sort of a challenge, because as comedy writers, we love having characters act mean to each other. So, Seth, his primary job was sort of policing the integrity of the Nerd and making sure that he is always in character. And then Matt [Senreich] and Seth both had sort of a policeman role when it came to our first draft of the outline. Tom, do you remember our first plot our first third act?

Sheppard: It involved killing the elves by a sexual act, I think.

Root: The Nerd and Santa Claus, in our first draft, figured out that all of the elves had been infected with the zombie virus and the only way to cure the virus was – because the virus was in a part of the brain that was chemically affected by sexuality, and so they figured out that if they masturbated each of these elves, by hand, they could cure them one by one. And so we had this really exciting montage – like an action montage –

Sheppard: There's a song called "Jack Off an Elf."

Root: Santa Claus and our Nerd just furiously jacking off elves.

Sheppard: We were very proud of this.

I'm sure your parents were, too.

Root: That outline went to Matt and Seth, and they came back and said, "You know, we really like where this is going, but let's work a little harder on that ending." [Laughs]

What's fun for you guys to do a Christmas episode every season?

Root: A lot of us are old enough to remember when there was sort of this dearth of good children's programming until you got to Christmas. And that's the only time would could see "Rudolph, the Red-Nosed Reindeer" or "[A] Charlie Brown Christmas." It was really exciting. And I think, now that we work in animation, it just seems like this natural thing that we always want to do a Christmas special and we don't have really any – It never seems like a chore to come up with jokes about Christmas or references to things we loved about Christmas when we were growing up.

I have to ask, because among all your great work, I'm especially fond of your "Star Wars" entries, and obviously interest in "Star Wars" is at a fever pitch right now: Are you guys in talks or actively planning, once you get a sense of the new movie, are you going to do something new?

Root: Yeah, I think we're sort of champing at the bit to get going on "The Force Awakens."

Sheppard: Definitely.

Root: We even wrote a sketch about the Nerd and his fears about what "The Force Awakens" could possibly be, and how it could go wrong. So we can't wait until we actually have something to play with. I can't guarantee we'll do a full special about it, but we're definitely going to do "Star Wars" sketches, as long as the show's on the air.

Do you have some more themed or sort of branded shows in mind? You've been doing great with the DC specials.

Root: We have at least one special that I don't think has been announced.

Sheppard: Yeah, I don't think we're allowed to say.

Root: So that news is coming, but we're definitely going to keep doing specials. The longer the show's on the air, the more we really crave the chance to break out of our format and do those specials, which break the mold of our normal show.

Beyond the holiday special, is there something you're really excited for the fans to see coming up? Is there something that you can't wait to see their reaction to?

Root: [To Sheppard] Well, what's coming up that's like super special, as far as–?

Sheppard: In terms of big spectacle? There are a lot of things, but some of the smaller things are exciting to me, like our "Dynasty," "Knott's Landing" and "Falcon Crest" sketch is– [Laughing]

Root: We can tell you that we have a "Duck Dynasty" sketch coming up, which will entertain nobody. [Laughs]

Sheppard: And confuse many.

Root: But some of the stuff that's made us laugh the most is just little things – like, we have a man go to the veterinarian to pick up his dog who's been neutered. He says his bulldog Brutus has been neutered and he's here to pick him up; and then out from the operating room comes Brutus, doing a full 1930s-era burlesque number with a feather boa and it sounds real stupid when I pitch it to you verbally, but when you see what our animator could do with a little bulldog and a feather boa, it's like, we could watch that on a loop all day long.

Sheppard: We've also got the [Last] Unicorn coming back, in a pretty big way.

Root: Oh, yeah, in a very long sketch. And we're going to touch upon "Breaking Bad" in a way that is going to be really unique. And that's actually one of our big showcase pieces that’s coming up later in the season.

Sheppard: And may include some of the cast of "Breaking Bad"

I will close out by asking, because your animators always do such an amazing job, is there something you want the super-sharp-eyed, freeze-frame viewers to look for in the animation of the Christmas special?

Root: Hmm, in the Christmas Special? [To Sheppard] Did they hide anything, like in Santa's workshop?

Sheppard: I don't think we did.

Root: I'd say pay attention to the set dressing in Santa Claus' office.

Sheppard: Yeah.

Root: Not necessarily Easter egg stuff, but fans of the – if there are any – of the ‘80s movie with Richard Pryor called "The Toy" will definitely pick up what we're laying down.

“The Robot Chicken Christmas Special: X-Mas United” airs Sunday at midnight ET/PT on Adult Swim.