"Trying to create the end of our show this season — because we had said this was the last season — was really difficult for us," star Kiefer Sutherland told fans Thursday, with EP Jon Cassar noting that the "24" movie is still "potentially" out there.

Fox kicked off Thursday with one (perhaps) final tribute to Jack Bauer, bringing Kiefer Sutherland to his first San Diego Comic-Con for the recently concluded limited series 24: Live Another Day.

The panel, which was moderated by exec producer/Jon Cassar, was an intimate conversation between the duo — and about 4,000 fans who were captivated by Suthlerland's every word, while executive producer Howard Gordon was a last-minute attendee and sat with the press.

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"We've made nine seasons of 24 together and this is the most nervous I've ever seen him," Suthlerland said of his co-pannelist to start the session.

The duo shared inside secrets about the series, including the challenges that came with filming in London for the first time.

"We needed six weeks to even have a gun on set, advance notice, etc., so that became kind of difficult. Having said that, there was a fantastic thing that happened out of that," Suthlerland said. "We had to start think about, 'Instead of killing somebody, how else can we be dramatic about that?' In the end, it was fantastic."

The duo also shared their fears of revisiting the beloved franchise for the ninth season, with Sutherland calling the role the "greatest gift" of his career.

"The panic was extraordinary," he said. "If you honestly ask any of us, over the course of eight seasons, we'll never say we made a perfect season, not for a second. But there was enough that we were proud of after eight seasons that we were really proud of what we did. So the idea of opening that up again and potentially damaging that again was really massive. For six months after we agreed to season nine, I turned myself inside out and into a complete mess. I remember the first three days when we were shooting, [asking], 'Is this anything like Jack Bauer?' I was so worried about not serving the character, the story and the franchise justice that I had done a number on myself."

Suthlerland also stressed that producers had a new kind of freedom to craft the ending that they wanted, and admitted — in a nod to the fact that Bauer survives — that on "some level … we copped out because it's hard to let it go."

"It's hard to end it. We came — ourselves, as people who are making the show — came full-faced with that," he said. "Trying to create the end of our show this season, because we had said this was the last season, was really difficult for us. All of us individually didn't want to let it go; we fought against it, we fought for it. Your response to the end of this season was really gracious and kind, so thank you very much."

As for the future of the series, that was not immediately addressed during Thursday's panel. However, Fox Networks Group chairman Peter Rice told reporters earlier this month that he and the show's producers haven't had a "specific conversation" about the series coming back yet. "I'm sure that we will in the future. It’s a wonderful franchise," he said at the Television Critics Association's summer press tour. "When you look at the show itself, it has many more stories to tell, but I think we have to sit down and talk to the creators about it."

Cassar did note that a 24 movie is still in the mix: "We're still talking about the movie; it's still potentially out there," he said from the Comic-Con stage.

Email: Lesley.Goldberg@THR.com

Twitter: @Snoodit