The new Batman movie “The Dark Knight,” opening today, is expected to be a global blockbuster. But a local guerilla promotion by a San Antonio theater chain threatened to turn that Hollywood cliché into a literal bomb.

To generate regional publicity for the film, the Santikos Theater chain mailed out cakes studded with wires and iced with a phone number and the message “Call Me” to 25 local TV, radio and newspaper outlets. The cakes had cell phones baked inside, along with promotional materials for the film.

When users dialed the number iced onto the cake, they were to receive a text message instructing them to come to one of the Santikos theaters premiering “The Dark Knight.”

The campaign was very similar to one used by the film’s studio Warner Brothers last fall to create buzz around the movie. But the staff at KENS TV5 didn’t make the connection and instead evacuated their studios for an hour or so after calling the police, the fire department and the bomb squad.

“I noticed it was in an unmarked box,” KENS assignment manager Sue Calberg told the press. “It was really dirty. The outside of the box had icing all over it. And the cake wasn’t a professional looking cake.”

The cakes were intended to be accompanied by an e-mail and video footage describing the purported kidnapping of the coyote mascot for the San Antonio Spurs basketball team. It was unclear at press time whether those additional materials had also reached the staff at KENS 5 TV.

Once the cake was investigated and the campaign’s intent uncovered, the San Antonio Fire Department’s arson bureau decided not to file charges against the theater chain, and employees were allowed back into the building.

“The intent was not to harm or cause an alarm,” SAFD Lt. Joe Rios was quoted as saying. “It just went bad on them.”

The cake “was intended to look like something the Joker would have sent,” Santikos spokeswoman Meghan Vincent told the press. “In this version of ‘The Dark Knight,’ the Joker is a very sinister fellow. So it was intended to look sinister.”

The Santikos chain also went so far as to spray graffiti on the theater that will begin showing “The Dark Knight” in San Antonio, scribbling “Why So Serious?”—a catchphrase of the Joker, played in the movie by the late Heath Ledger.

The staff at KENS 5 TV came in for some ribbing from other local media outlets that were quicker to pick up on the promotional nature of the cakes. The San Antonio Current, a free newsweekly, said in its online blog that it had also received a wired cake.

“Did we panic?” editor Ashley Lindstrom asked in a blog post. “No…We were wondering why we hadn’t gotten one sooner, truth be told. We’ve been reading about this sort of thing happening in other cities since before Christmas.”

The moral of the story, Lindstrom suggested, might be that “it’s always handy to have a 25-year-old fanboy or girl around to prevent the needless dispatch of law-enforcement officials.”

In February 2007, electronic lightboxes placed around Boston to promote a movie based on the “Aqua Teen Hunger Force” characters ran into the same generational gap when subway workers reported finding one of the devices under an overpass in Charlestown, Mass.

That case resulting in arrest charges against two local artists involved in placing the devices and a $2 million settlement with Turner Broadcasting, which owns the late-night Adult Swim animated channel that airs the ATHF series.