With the "Ghost Rider" storyline that served as the first arc on the fourth season of "Marvel's Agent of S.H.I.E.L.D." now complete, the series' creators are opening up on how including one of the comic book company's best-known and most-loved characters was a major game changer for the show.

CBR was on the set of the Marvel Studios series as executive producers Jeffrey Bell and Jed Whedon revealed that while they've interpreted a few familiar characters from the comic book universe -- Mockingbird, Quake, Deathlok, Mr. Hyde and the Absorbing Man among them -- building a major storyline around the supernatural Spirit of Vengeance was a different experience altogether. Ghost Rider was first created in 1972, often a top-selling marquee headliner in various incarnations and the subject of two motion pictures (in 2007 and 2012) starring Nicolas Cage.

"We were thrilled," Bell said. "We have to deal with the movie people and the television people, and we all negotiate for what we get. Sometimes they go, 'You can have Left-Handed Man.' This last year we said that we'd like to do something special, and they said, 'How about Ghost Rider?' We were like, 'He's cool -- but does he fit in our world?'"

The timing turned out to be fortuitous, as the producers were interested in tying the more technologically driven series to the film side's major, magic-centric fall theatrical release. "What helped us this season was 'Doctor Strange' coming out, where it opened doors to other kinds of storytelling within the Marvel Universe," Bell said.

"Yes, there's science, but less of it," he continued. "There's a lot of stuff in quantum physics that ties to Eastern religion and ties to a lot of the stuff that's in 'Doctor Strange.' We've tried to lean into that as well which has allowed us to tell Robbie and Dark Dimension stories, as opposed to going to a hell-world, you're in a different dimension, and there's science to back that up. We didn't make it up."

The Marvel powers-that-be gave the producers relatively free rein in terms of how -- and which -- Ghost Rider would be used, given that there have been three major modern incarnations of the character: Johnny Blaze, the original, featured in the Cage films; Danny Ketch, the wildly popular '90s-era version; and the most recently created Ghost Rider, Robbie Reyes.

"We chose Robbie," Bell said, of the show's Ghost Rider, played by Gabriel Luna. "Robbie was the one we wanted. Part of that was it felt like more our show. We liked that it was a kid from East LA. We liked that he had a brother. We liked that his brother had special needs. We liked that it hadn't been explored. However people feel about the 'Ghost Rider' movies, there's a preconception of that, and we didn't want to be compared apples to apples that way."

"We think with Gabe we found a really soulful character," Bell added. "[There's] the idea that Robbie isn't down with what's happening. It's like he wanted that atonement, and now there's a weariness to it. There is a sadness to the character -- as opposed to, 'I'm kicking ass and I'm a vengeance guy' -- that Gabe really inhabited, and I think really grounded him in a way. I think all the choices that Gabe made helped ground him, where the Nic Cage version is a very much larger-than-life version. So it allowed us to distance ourselves, simply, so he was our own."

"I have to say, everybody at Marvel, and Jeph Loeb especially, trusted us with it," Whedon said, "in a way that we thought that we would have to deal with a lot more of 'OK, here are the rules that come with Ghost Rider," because Marvel cares a lot about their properties, but they were very trusting with us."

"It allowed us to explore what we wanted to do with the character," Whedon added. "We weren't hamstringed in any way. I've got to hand it to them that it is a big property, and they just gave it to us and said, "Let's see what it is,' and it was a pretty easy process. We have to thank them for that."

"The thing that they asked was for us to be true to what it is," agreed Bell. "So though the way he's haunted by Eli in the comic is different than the way we did it, we still made Eli the bad guy. We took the same elements and hopefully freshened it up so for people who knew the show, they would be satisfied, as opposed to just waiting for the inevitable thing to happen."

While the initial "Ghost Rider" story has met its conclusion, there's been enough ambiguity to Robbie's fate that he may yet return, skull a-blazing. But the boundaries between magic and science that have been broken down will continue to be a key aspect of the next story arc, "LMD," which focuses on the true nature of the enigmatic A.I. Aida.

"One of the things that we're doing with the Aida story is we've seen how science was somehow tied into Robbie's origin, or at least the origin of his villains, and how that dovetails," Whedon said.

"Yeah, it's not an accident that his uncle worked in a lab that was dealing with quantum energy and things like that," Bell noted.

"So now as we go down this other story, we can go on a different journey," Whedon said, "but we are still playing in the same world, and these things could link up later in some way, and maybe in thrilling fashion."

"I feel this year we're getting to play with a lot of the toys that we've been hoping to play with," Whedon added. "And as we move into the second pod, there's another one in play, which is something that we've been wanting to get to and now we're finally able to get to.

"In terms of how it will feel and how big of a transition, we want everything to feel like its own mini-world, and to have its own flavor," he continued. "So we do think you'll come into the next section and immediately feel like, 'Oh, this is a different kind of story.' So we're excited about that."

"Marvel's Agents of S.H.I.E.L.D. returns Tuesday, Jan. 10 on ABC.