This fall, the Marvel Film Universe will take a major step forward in its expansion with the anticipated new ABC series "Marvel's Agents of S.H.I.E.L.D." The show produced by "Avengers" director and Marvel film mastermind Joss Whedon is both a big moment of payoff for the studio and a significant risk. In expanding the world established in films like "Iron Man" and "Captain America," the live action side of the comics company takes its first steps towards more direct serialized storytelling and world-building a la their four-color successors. But with the mysterious return of Clark Gregg's Agent Coulson leading the charge, the question is whether comic fans and general audience Marvel followers will be willing to go along with the deep Marvel U.

This Friday at Comic-Con International in San Diego, Marvel pulled out the stops in winning over audiences before the fall debut with a big panel in Ballroom 20 of the show. Featuring Whedon, Gregg, Marvel Head of Television Jeph Loeb and many more, the event promised to make some major reveals about the story of "S.H.I.E.L.D." and how it will fold back into the upcoming Marvel movie slate.

Loeb took the stage first and played MC for the panel, starting with a joke to the audience where he took off his jacket complaining of the heat to show off the back of his "S.H.I.E.L.D." t-shirt which read "Coulson Lives." After a round of applause, Loeb thanked Marvel's partners from ABC TV Studios who are co-producing the series - all a part of the Disney corporate family. After leading the audience in a chant of the premier date -September 24 -things got underway.

Writers/executive producers/show runners Jed Whedon and Maurissa Tancharoen took the stage then, followed by writer Jeff Bell. "You guys know some stuff," Loeb said then, hinting that even diehard fans who have been following news of the show weren't all caught up. Then he introduced "Agent Fitz" and "Agent Simmons" whom Loeb said most of the producers thought was "Agent Fitzsimmons" in early discussions, but Ian De Caestecker and Elizabeth Henstridge then took the stage followed by Chloe Bennett who plays "Sky," Brett Dalton as "Agent Ward" and Ming Na who plays "Agent Melinda May."

Loeb then introduced Agent Coulson himself as Clark Gregg took the stage to thunderous applause. The producer called the star whose character died in "Avengers" the reason it's "a pleasure to go work every day." Lastly, Joss Whedon came out to an equal standing ovation from the crowd, and then talk got underway.

Things went right into fan questions with the first asker being a little boy in a Two-Face costume who came to the panel thanks to the Make A Wish foundation. He wanted to know if any of the heroes from the Marvel movies would appear in the series, though Whedon played coy on the issue. Another fan, dressed as Deadpool dressed as Waldo, came up and asked whether Deadpool may appear on the series. Loeb said that "probably wasn't going to happen."

Then a young lady came to the mic to ask if there were any clips to share. "There was a whole legal thing with lawyers," Whedon mock apologized for having no clips before finishing "So we can't show you a clip. We're just going to show you the episode."

SPOILER WARNING: Some slight spoilers for the pilot episode lay ahead.

Without giving away any of the major reveals or moments, "Marvel's Agents of S.H.I.E.L.D." is tonally very much in line with the banter effect of Joss Whedon's "Avengers" screenplay. Here, the focus is on building a new team of Agents meant to be the front line in dealing with the growing super powered population on earth from the mysterious Melinda May to the young hotshot Ward. Coulson is the anchor for the tone and plot of the show as the team tracks down a rogue superhero -whose origin and powers have been much speculated about online, though we'll leave particular of his story out for now -and the Agent's mysterious return is addressed in the pilot. But as with many things in an espionage-themed show, there were plenty of plot points set up as mysteries to be explored later including the powerful villains behind the group Rising Tide.

Overall, one noticeable facet of the show was the level of references and in jokes for comic fans and Marvel heads. "Agents of S.H.I.E.L.D." may be the only TV series this pilot season with casual references to cosplay, for example. Being Comic-Con, the jokes and notes in the pilot to both Marvel films and comics played well with the fans.

And many may be interested to note that when credits rolled, after the directing credit for Joss Whedon and the writing and executive producing credits for the creative team, one of the first credits top lining the series was one for S.H.I.E.L.D. creators Stan Lee and Jack Kirby.

After the screening was done, the panel returned to the stage, and Loeb asked Gregg what it was like to be back. "I didn't like being dead, but I really loved my death. I never though anything could top that," the actor said, calling himself a longtime Marvel fan. "I got a call from Marvel saying, 'You've really got a great part in Avengers' and I thought 'Oh, great! Awesome!' And then they said, 'Yeah, what happens to you is what brings them to get together' and I was like 'Whaaa?'" He went on to say that the "Coulson Lives" phrase started as a fan hashtag - a phrase of support that he was sincerely appreciative of. The plan for his return -and for his new car in the series -convinced him to come back to action, but all he would say about the show moving forward was "Wait 'til you see episode 2."

Fitz and Simmons were up next as Henstridge joked that their UK accents apparently make the techies of the series sounds smarter than the actors were. The frequent bit for the characters is talking over each other as they rapid fire discuss the super science of S.H.I.E.L.D. Meanwhile, Bennett recalled her having to audition six times before getting the part of everywoman hacker Sky.

Na spoke to the fact that her Agent is set up with a mysterious past that takes her out of action before the show begins, though she kept mum on what that past could be. And as opposed to her well known past on NBC's "ER," Dalton spoke about being a total unknown to fans everywhere, laughing that no one would call him "'Killing Lincoln's' Brett Dalton." Na said she got chills listening to fans in the room react to the pilot.

The writers were simply glad to have something out there after months of keeping secrets on behalf of Marvel. Bell joked that they were spending way too much money on new episodes of the show. Then Jed Whedon spoke to the key contributions of Bear McCreary and his score.

Joss Whedon wrapped by simply thanking the fans for allowing Marvel to continue this grand storytelling experience.

"Marvel's Agents of S.H.I.E.L.D." airs September 24 on ABC.