Sonys R-rated stoner comedy "Pineapple Express" lit up the box office on Wednesday, grossing $12.1 million from 3,072 theaters to toke on the best Wednesday opening ever for August.

Girl favorite "Sisterhood of the Traveling Pants 2" also enjoyed a sterling midweek bow, grossing $5.7 million from 2,667 runs, according to Rentrak. The Warner Bros. and Alcon Entertainment sequel is well on its way to eclipsing the $9.8 opening weekend gross of the first "Sisterhood."

For the first time in its run, Warners "The Dark Knight" came in No. 3 for the day, behind "Pineapple Express" and "Sisterhood."

The Batman sequel still showed a spectacular hold in its 20th day in release, grossing $5 million from 4,128 theaters for a domestic cume of $410.8 million.

"Pineapple Express" easily blew by the $8.9 million earned by "The Princess Diaries 2," the previous record holdover for best Wednesday opening in August. Whether "Pineapple Express" can roll enough coin to beat "Dark Knight" for the weekend itself is now the question.

"Pineapples" opening-day gross of $12.1 million virtually matches the $12.3 million earned by Judd Apatow-produced "Superbad" on its first day in August 2007; the difference is that Sonys "Superbad" opened on a Friday. "Pineapples" Wednesday performance came in ahead of expectations.

Starring Seth Rogen and James Franco, "Pineapple Express" is the second R-rated comedy produced by Apatow to enter the market in under two weeks, after Sonys Will Ferrell-John C. Reilly starrer "Step Brothers."

"Step Brothers" fell to No. 6 on Wednesday, declining 23% from the day before to $1.9 million from 3,109 runs. Thats a bigger day-over-day decline than the other films in the top 10 saw on Wednesday, suggesting that "Pineapple" is taking a bite out of its aud. Cume on "Step Brothers" is $70.2 million.

Us "Mamma Mia!" dropped only 5% to $2.3 million (cume: $94 million), while "Dark Knight" declined 10%. Us "The Mummy: T**** of the Dragon Emperor" placed No. 4 on Wednesday, grossing $3.2 million from 3,760 for a cume of $51.7 million in its first five days in release.

While "Mamma Mia!" coming in No. 5 on Wednesday continues to benefit from female attention among all age groups, "Sisterhood" appeals to teen girls and tweens. Sequel, also produced by Denise Di Novi, reunited the cast from the original film, America Ferrera, Alexis Bledel, Amber Tamblyn and Blake Lively.

In the time since the first "Sisterhood" was in theaters, both Ferrera and Lively have become stars of hit TV shows.

The first "Sisterhood" pic, released on a Wednesday in early June 2005, grossed $2.1 million on its first day on its way to cuming $39 million domestically.

On the foreign front, "The Mummy:T**** of the Dragon Emporer" should remain the dominant player

following an impressive $61 million launch weekend in 27 markets. The actioner's heading into two dozen additional territories, including France, Germany, Scandinavia, Taiwan and the U.K. Three days of weekday biz gave "Emporer" a foreign cume of $80.6 million, led by $17 million each from Russia and South Korea. "The Dark Knight" will also keep international biz humming after grossing $38 million from 51 holdover territories last weekend to cross the $200 million mark in foreign grosses -- well above the final offshore cumes of the five previous Batpics. "Knight" swoops into South Korea and

Spain this weekend -- the same markets in which Disney's "Wall-E" opens. The Pixar toon's still early in its foreign run with international cume at about $100 million from two dozen territories. Sony's going day-and-date with "Pineapple Express" in Australia, but won't open the stoner comedy in Europe until the fall. U's "Mamma Mia!" continues to impress overseas with foreign cume hitting $155 million from 22 markets as of Wednesday, led by a jaw-dropping $70 million in the U.K. It's launching in the Czech Republic and Slovakia. Other launches include "Forgetting Sarah Marshall" in Poland, "Prom Night" in Mexico, "X-Files: I Want to Believe" in Holland and Mexico and "You Don't Mess With the Zohan" in Holland.