• "Five Nights at Freddy's" grossed a surprising $78 million in its domestic opening weekend.
• The movie benefited from a PG-13 rating, which helped draw in its younger fanbase.
• It was the second-highest opening weekend for a video game adaptation.

If anything was going to topple Taylor Swift at the box office, it had to be a killer animatronic bear, right?

"Five Nights at Freddy's," the new Universal-Blumhouse horror offering set in an abandoned Chuck E. Cheese-type kids' pizza parlor, scored an estimated $78 million at domestic theaters over the weekend, a huge haul that surprised many in the industry. Swift's "Eras Tour" concert film came second for the weekend, with an estimated $14.7 million, putting its domestic total at $149.3 million.

"Five Nights at Freddy's" had a few things going for it. First, it was Halloween weekend, primetime for spooky movies. In fact, the flick made more in its first weekend than fellow Universal-Blumhouse horror collaboration "The Exorcist: Believer" has made in its entire domestic run so far (an estimated $59.4 million, according to Comscore).

"Five Nights" is also based on a popular horror-survival video game series that gave it a built-in younger audience. That helped it overcome generally awful reviews that left the film with a 26% "rotten" rating on movie-review aggregator Rotten Tomatoes.

Data firm EntTelligence said the movie accounted for 65% of foot traffic to theaters during the weekend. Audiences liked it, as well, giving it a strong A-minus rating, according to Cinemascore.

The movie's PG-13 rating no doubt helped parents decide to let their kids see it, vindicating director Emma Tammi's decision to make it a "gateway" horror movie for youngsters. (Don't count on an R-rated cut, either.)

"The success of 'Five Nights' was the culmination of many factors not the least of which was making the film accessible to younger fans via the less restrictive PG-13 rating," said Paul Dergarabedian, senior media analyst at Comscore.

The "Five Nights" fanbase propelled it to the third-biggest domestic opening weekend for a horror movie, behind both chapters of Warner Bros.' recent "It" movies. It also cleared the bar set by 2018's "Halloween" as Blumhouse's biggest opening, according to Universal.

Fans also gave it the second-biggest weekend ever for a video game adaptation, behind Universal and Nintendo's "The Super Mario Bros. Movie," which grossed more than $146 million in its first frame earlier this year.

"Given the high level of interest by teen audiences, these key moviegoers were clearly inspired to migrate from their gaming small screens to the big screen to enjoy a communal, in theater experience that drove weekend grosses to much higher than expected levels for 'Freddy's,'" Dergarabedian said.

The movie scored success at theaters even as it premiered on Peacock, NBCUniversal's streaming service, at the same time. Universal said the movie is on pace to have the biggest-ever opening on the streamer.

Disclosure: NBCUniversal is the parent company of Universal Pictures, Peacock and CNBC.