It’s likely that many filmgoers who saw J.J. Abrams’ nostalgic sci-fier “Super 8,” which came away this weekend with an estimated $37 million, didn’t know what to expect before visiting the multiplex — Paramount purposely kept tight-lipped about key plot details.

But Par’s less-is-more gamble apparently paid off, as “Super 8” managed to outdo industry expectations, which topped out at around $30 million.

“Super 8” amassed most of its weekend traffic on Saturday, driven by building word of mouth, said Par vice chairman Rob Moore.

The film’s sneak screenings on Thursday (which took $1 million) effectively increased audience awareness throughout the weekend; social networking sites like Twitter had been used to promotethe sneaks. Par struggled early on to establish widespread interest in “Super 8” because of the studio’s super-secretive marketing campaign. Cume is $38 million including sneaks.

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The sci-fi homage lacked the opening oomph that most bizzers had expected, especially for a summer blockbuster. But weekend-to-weekend totals were down only 5% vs. the same frame in 2010.

Thanks in part to social networking, Moore said “Super 8” was able to catch on the way Sony sci-fier “District 9” did when it opened to $37.4 million in August 2009. “Word of mouth doesn’t take weeks to spread anymore,” Moore said. “It takes hours.”

Par has been at the forefront of using social media to tubthump releases. Studio partnered with Twitter in March to launch the trailer of “Super 8” before teaming again to pay for a “Promoted Trend” placement for Thursday’s sneaks at 324 Stateside locations, including all 239 Imax theaters. (Pic went on to gross $500,000 later that day from approximately 1,200 midnight screenings.)

Imax provided a significant boost to the “Super 8” weekend tally, contributing a total $4.4 million with a strong per-screen average of $18,410. “Super 8” also saw a better-than-usual Friday-Saturday uptick at Imax locations just as it did overall.

“As summer blockbusters go, this movie’s a turtle rather than a rabbit, and the healthy bump from Friday to Saturday reflects that,” Imax prexy Greg Foster said.

Debuting alongside “Super 8” in regular multiplexes, Smokewood Entertainment’s kidpic “Judy Moody and the Not Bummer Summer” played to expectations with an estimated $6.3 million, hampered by its appeal to a narrow demo slice — girls 6-11. Relativity Media is distribbing the pic, which cost Smokewood a reported $20 million, through a service deal on behalf of the film’s producers.

In its second frame, 20th Century Fox’s “X-Men: First Class” dropped to No. 2 with an estimated weekend take of $25 million, off 55% from last weekend; cume is just shy of $100 million. “First Class” is playing slightly ahead of its franchise originator, which fell 57% during its soph sesh and cumed $157.3 million domestically.

The Fox pic put up a good fight for the weekend’s overseas crown, posting an estimated $42.2 million from 66 markets. But the film ultimately lost to Paramount-DreamWorks Animations’ “Kung Fu Panda 2,” which added 17 new markets for a total 45, where it grossed $56.5 million — the weekend’s best take overseas.

“First Class” has totaled $124.2 million in two weeks, while “Panda 2” cruised passed the $200 million mark internationally in its third week.

Domestically, “Panda 2,” down 30%, had the weekend’s second-best hold after Universal’s resilient “Bridesmaids,” which dropped just 16% in its fifth frame. “Bridesmaids” has stacked up extremely well in holdover frames, providing a hopeful — albeit less obvious — comp for “Super 8,” according to Par.

U’s bawdy femme-driven laffer opened to $26 million, which was what most B.O. observers had pegged for “Super 8.” Like “Bridesmaids,” “Super 8” landed during a busy summer sked, with high-profile titles looming after its opening weekend.

But Moore opined that “once a movie gets embraced by moviegoers, it’s not driven by marketing anymore but by those moviegoers.”

“Super 8” played best with auds over 25 (71%) but saw a fairly even split between genders, with men accounting for 56% of the pic’s opening. “We knew the sweet spot to start was going to be people 30-50,” Moore said. He expects the film to broaden to younger auds based on positive word of mouth and the film’s social media following. (Under-25 auds gave the pic an A- CinemaScore rating vs. its overall B+ rating.)

Par’s 2010 Christmas pic “True Grit,” which cumed domestically $171 million, eventually played much younger compared to when it first debuted.

Sony Pictures Classics continued its success with the rollout of Woody Allen’s “Midnight in Paris.” Pic expanded wide on Friday to 944 locations. Weekend total was an estimated $6.1 million, enough to put the film in the top 10 for its second straight week. Cume is $14.2 million through Sunday.

Also doing well at the specialty B.O., Focus Features’ “Beginners” saw a 76% uptick from Friday to Saturday — the usual bump is 50%-60%. “Beginners,” which collected $254,587 in its second week, scored a healthy $13,399 per-screen average from 19 locations, up from four last weekend.

Meanwhile, IFC’s six-theater launch of Michael Winterbottom’s comedy “The Trip” opened strong with an estimated per-screen average of $14,100 and a weekend total of $84,600. IFC plans to expand the film to the top 20 markets on Friday.