SAN DIEGO — The hordes of zombies, legions of Stormtroopers, leagues of superheroes and crews of Starfleet officers have already begun crawling, marching, flying and beaming into San Diego for that other big convention this week: Comic-Con International.

The pop-culture celebration is kicking off Wednesday evening with the festival’s preview night, where con-goers with four-day passes have first crack at the collectables, free swag and photo opportunities on the San Diego Convention Center floor.

Outside the sprawling bayside venue, the world premiere of “Star Trek Beyond” is being held Wednesday night at the Embarcadero Marina Park. The sci-fi sequel’s U.S. debut will mark the first-ever outdoor Imax screening.

Comic-Con is expected to draw more than 160,000 fans for high-energy sessions featuring casts and crews from such films and TV shows as “Game of Thrones,” ‘’Star Trek,” ‘’Suicide Squad,” ‘’South Park,” ‘’Teen Wolf,” ‘’Aliens” and “The Walking Dead.”

“I think the most important thing is for all of us to be there and acknowledge the fans’ support and passion,” said “Aliens” and “The Walking Dead” producer Gale Anne Hurd. “Obviously, we’ll have a (“Walking Dead”) promo and will premiere it in San Diego, but it’s that connection to the fans that Comic-Con is really all about.”

The festival will likely provide attendees with some never-before-seen surprises, as well as exclusive glimpses at such upcoming entertainment entries as “Wonder Woman,” ‘’Guardians of the Galaxy Vol. 2,” ‘’Valerian and the City of a Thousand Planets,” ‘’Riverdale” and a new “Star Trek” show.