Keanu Reeves and Jennifer Connelly have teamed up for a modern-day remake of the '50s sci-fi classic 'The Day the Earth Stood Still,' in theaters December 12, and the star duo landed in San Diego to preview their movie for Comic-Con fans!

"This is like the mecca -- this is the place to begin," Keanu tells ET about unveiling his new movie to the die-hard fans.

"I've never been here before, but I've heard so much about it," says Jennifer.

In the movie, Keanu plays Klaatu, a humanoid alien who lands on earth to warn world leaders -- with the help of an indestructible robot -- to stop warring or the human race will be annihilated by watchers from above. Jennifer is the woman who may hold the key to mankind's survival, and Will Smith's son Jaden Smith is also featured in the film!

"This film has more spectacle, more visual effects, so it should be exciting," says Jennifer, who promises that the "essence" of the original will remain intact.

The original 'The Day the Earth Stood Still' capitalized on the growing fears in the post-war atomic age and made the giant silver robot "Gort" one of the most iconic images of '50s sci-fi.

"We all loved the original film; it's really a wonderful classic, and [our film] was made with the utmost respect for that," says Jennifer.

More than 125,000 fans are expected to attend ComicCon from Thursday to Sunday to get exclusive sneak previews and the newest info on their favorite movies, TV shows and comics, as well as to buy, sell and trade comic book, TV and movie-related merchandise -- and dress up like their favorite characters!