Jon Favreau was relieved that the season finale of 'The Mandalorian' was not leaked

"The Mandalorian" creator Jon Favreau says he is relieved that the show's major reveal for the second season was not leaked to the public.

Season two of the Disney Plus series wrapped on December 18 with a surprise appearance by "Star Wars" veteran Mark Hamill as the de-aged Jedi master Luke Skywalker in the final moments of the last episode.

During his virtual appearance on "Good Morning America", Favreau said Hamill was actually present on the show's set to shoot for the sequence.

"We started off the whole series with the Baby Yoda reveal – with the Grogu reveal – that was a secret that everybody was really blown away by. Part of that is not telling too many people, not having merchandise that’s being tooled up and announced and everything.

"And then the very last episode having Mark Hamill actually on set filming and us using whatever technology we had available to de-age him and try to make him look as much like he did in the old films," he said.

Favreau stressed maintaining a secret from the eagle-eyed fans of the "Star Wars" universe is a difficult task.

"It was very tricky because it’s very hard to keep a secret nowadays, especially with 'Star Wars' because people are so curious about it. And there are so many people involved with the process with visual effects finishing, making it, filming it, the studios everything.

"Every piece of casting leaked, and we were so scared right up until it aired that our surprise cameo was gonna leak too," he added.

After the season finale's premiere, Hamill had himself celebrated on Twitter that his appearance as Luke Skywalker wasn't leaked.

"The fact that we were able to keep my involvement a secret for over a year with no leaks is nothing less than a miracle. A real triumph for spoiler-haters everywhere!" he posted on the social media site on Sunday.

A "Star Wars" spin-off series, "The Mandalorian" is set after the fall of the Empire and before the emergence of the First Order. Fronted by Pedro Pascal, the show depicts a lone bounty hunter in the outer reaches of the galaxy far from the authority of the New Republic.

It also features Carl Weathers, Werner Herzog, Taika Waititi, Gina Carano, Giancarlo Esposito and Nick Nolte.