It’s the 20th anniversary of “The Sixth Sense,” a success that took everybody by surprise, including the filmmakers. Writer-director M. Night Shyamalan had made only two films, “Praying With Anger” and “Wide Awake,” which barely made a ripple in theaters. However, Variety reported Aug. 9, 1999, “In a surprise ending to rival the film’s twisty plot, Buena Vista’s supernatural thriller ‘The Sixth Sense’ stunned prognosticators by snatching the weekend box office title from odds-on favorite ‘The Blair Witch Project.’ The Bruce Willis starrer opened to an August record $25.8 million, according to studio estimates.” A month later, Variety declared it the “Sleeper of the Summer,” and said amid all the films with big marketing budgets and the studios’ newfound fascination with internet promotion, “Sixth Sense” had an old-fashioned reason for success: “This film has spectacular word of mouth,” Marc Pascucci, senior VP of marketing for Loews Cineplex U.S., told Variety.

The film had been set to open in October, but the studio took a big gamble and opened it Aug. 6, thinking that it might do some business as summer was winding down.

A few days before the film’s opening, Variety’s reviewer predicted good box office, though he was unimpressed by the film itself, finding it “a mostly ponderous tale — moody, low-key and semi-pretentious without being scary or suspenseful for most of its running time.” He also marveled at the fact that “Few pictures have hinged their effectiveness so completely upon information withheld until the last moment” and said the pic might be “more rewarding upon second viewing.”

Indeed, many audience members flocked to repeat views. On Sept. 8, 1999, Variety printed a package of stories analyzing the past summer; box office maven Ben Fritz began his story about “Sixth Sense” by describing the low expectations, in light of the other offerings at the multiplex. “If women and couples were going to ‘Runaway Bride,’ the teens and hipsters to ‘Blair Witch’ and the male action fans to ‘The Thomas Crown Affair’ and ‘Mystery Men,’ who would be left to see a film whose trailer tagline was an 8-year-old saying ‘I see dead people?’ The answer, in retrospect seems obvious: Everyone.”

Fritz said “Sixth Sense” benefitted from “largely positive reviews, a savvy marketing campaign that emphasized the film’s intelligent scares and a family-friendly PG-13 rating” — and, of course, word of mouth. He pointed out that the Hollywood Pictures/Spyglass Entertainment film not only won its opening weekend, it stayed at No. 1 for the next three weeks, with only modest declines.

Globally, it earned $673 million, the second biggest hit of 1999 after “Star Wars: Episode 1 — The Phantom Menace.” And the film was nominated for six Oscars, including best picture, director, writer, editor (Andrew Mondshein), and supporting actors (Haley Joel Osment and Toni Collette).