Thursday kicked off a celebration 40 years in the making — with surprise guests and a touching tribute to Carrie Fisher

The 40 Years of Star Wars panel at Star Wars Celebration featured generations of castmembers from a galaxy far, far away to mark the 40th anniversary of Star Wars: A New Hope, which opened in May 1977. 

Surprise guests George Lucas and Harrison Ford sparked pandemonium, while Lucasfilm president Kathleen Kennedy was joined by previously announced guests Mark Hamill, Anthony Daniels, Ian McDiarmid, Peter Mayhew, Billy Dee Williams, Warwick Davis and prequel star Hayden Christensen.

Davis hosted the festivities, introducing a behind-the-scenes reel looking back at how 1977's A New Hope launched a phenomenon. 

In a tear-jerking moment, an interview with Carrie Fisher played over footage of her hugging fans.

"It's about family, and that's what's so powerful about it," said Fisher. "They are showing the films to their children and their grandchildren. They're sharing something that moved them as a child."

Kennedy took the stage to thank fans who camped out on the street for a seat to the panel and make a surprise introduction of Lucas. Davis and Lucas sat down and took a moment to acknowledge Fisher and the late Kenny Baker, who played R2-D2 and died in August 2016.

Lucas admitted his pitch for Star Wars may have seemed outlandish — after all, it involved "dogs flying space ships." But he was appreciative of the studio for taking a chance on it.

"The idea was to do a high adventure film that I loved when I was a kid with meaningful, psychological themes," said Lucas. 

Lucas admitted he wasn't supposed to say this, but he described A New Hope this way: "It's a film for 12-year-olds."

"You're 12 years old. You're going to go on in the big world. You're moving away from your parents being the center focus. You're probably scared, you don't know what's going to happen, and here's an idea of some of the things you should pay attention to. Friendships, honesty and trust — and doing the right thing. Living on the Light Side. Avoiding the Dark Side."

After speaking about seeing how excited kids were while they were shooting 1999's Episode I — The Phantom Menace in Spain, Lucas said of critics and certain fans, "They're not very kind, but when you see these little kids and the look on their face and what it means to them," that makes up for everything. 

Star Wars Rebels executive producer Dave Filoni then came out to speak with Lucas about bringing the franchise to TV. 

"I'd done Indiana Jones for television, and it's a great experimental cauldron because there's not that much at stake," said Lucas. "You're not saying, 'Here's $100 million. It's all on your shoulders.'" 

Next, Liam Neeson (Qui Gon Jinn) appeared via video for a special announcement.

"We're making a very unofficial movie about Jar Jar Binks and what happened to Jar Jar. Spoiler alert: He did go to the Dark Side," the Phantom Menace star joked. 

Then Sith lord and apprentice McDiarmid and Christensen reunited onstage, where Christensen spoke about his epic volcano lightsaber battle in Episode III and the unexpected challenge it presented.

"I had been conditioned from a very young age to make the sound effect when I swing the lightsaber … it was a difficult habit to break," said the actor of playing Anakin Skywalker.

Lucas would have to come tell him after takes, "I can see your mouth moving."

"I was so focused I wasn't aware I was doing it," said Christensen.

Another prequel star, Samuel L. Jackson, made a video appearance to pitch a return for his dearly departed Jedi Mace Windu, who died in Episode III. He noted Star Wars has a long history of Jedi returning for future installments beyond their deaths or returning with cybernetic limbs.

"I am not dead … Mace Windu is awaiting his return. Let's make it happen. Kathy you're sitting right there," he joked, addressing Kennedy.

C-3P0 actor Daniels, shared his favorite Lucas story — noting that early in shooting on A New Hope, he was flummoxed when he realized while shooting that R2-D2 wouldn't be making any sounds on set.

"When I finish my line, could you make a sound? Could you go 'beep.' And you went, 'Sure. Beep.' And I decided I was better off on my own, George," said Daniels. 

Finally, the hero himself arrived.

Hamill joked that Star Wars fans were more supportive than his actual family, and Lucas spoke about how hard it was to cast Luke Skywalker and the rest of the key roles for Star Wars, saying it took a year of testing.

"We had two or three of each of you, and you would each test with another person until we found the combination of the group that worked the best together," said Lucas. "The group that was ready to be an ensemble and that played as old friends." 

Then, an even bigger surprise: Ford, an unannounced guest, took the stage — and Davis took time to make a joke about Ford's recent piloting woes

"I can't believe we managed to keep it a secret, considering you landed your plane on I-4," said Davis.

Ford quipped back: "Yeah, but it was a good landing." 

The panel concluded with a remembrance of Fisher, with Lucas delivering an emotional tribute.

"She played a part that was very smart, and she was having to hold her own against two big lugs, goofballs that were screwing everything up. She was the boss. It was her war, and when I cast it, I said I want somebody young to play the part. I want somebody very young. When Carrie came in, she was that character. She was very strong, very smart, very funny, very bold, very tough, and there really wasn't much of a question. There are not very many people like her. They are one in a billion. For this particular part, it was absolutely perfect. … She wore a dress through the whole thing, but she was the toughest in the group," said Lucas." It really shows the level of her talent, and at the same time she was fun to be with. … She was very challenging in terms of pointing out that certain pieces of dialogue were a little hard to say. She was brilliant and obviously we will all miss her, but she will always be the princess who took command and never backed down, never was in jeopardy. She was always helping the other guys get out of the messes she created. We'll all love her forever and ever."

Fisher's daughter, Billie Lourd, also took the stage to honor her mother and introduce a video tribute, which was followed by an impromptu concert conducted by Star Wars composer John Williams.

Here's what Chris Hartwell, Heat Vision's eyes and ears in Orlando, says of sitting in the audience: "It was great way to kick off the convention. Nothing revelatory, but it totally sets the mood. We're here to honor the past — the '77 film and those that are no longer with us (like Carrie Fisher) — and look to the future: The Last Jedi and all of those films after it and all the new fans that it will bring in."

Star Wars Celebration is taking place Thursday through Sunday.