Well, it's official. Moviegoers love Melissa McCarthy.  After the unexpected blockbuster box office for "Identify Thief" in February, McCarthy teamed up with Sandra Bullock for the R-rated comedy "The Heat" this weekend. The Paul Feig flick opened to a larger than expected $40 million and is a career best for both McCarthy and Oscar winner Sandra Bullock. And yet "The Heat" still couldn't take the top spot at this weekend's box office.

Walt Disney Studios and Pixar's "Monsters University" remained at no. 1 with another $46.1 million and an impressive $171 million in just 10 days. At this rate "MU" should easily match "Monsters' Inc.'s" $289 million cume back in 2001. Competition from "Despicable Me 2" on Wednesday will knock it from the top spot, but it's a huge success for Disney who still has the no. 1 movie of the year in "Iron Man 3."

Dropping to no. 3 was Paramount Pictures' zombie action flick "World War Z." The Brad Pitt flick grossed $29.8 million for $123.7 million to date.  With a $190 million pricetag, however, Paramount is going to need for international grosses to substantially cover the film's production and marketing budgets if they really think a sequel is feasible.

Debuting in fourth place was Roland Emmerich's "White House Down" with just $25.7 million. That disappointing result was in the range of pre-release polling, but Sony Pictures was no doubt hoping for a larger gross. Even with Channing Tatum and Jamie Foxx in the mix moviegoers were not convinced "White House Down" was a must-see against formidable competition. It's still unclear whether March's similarly themed "Olympus Has Fallen," which opened to $30.3 million, factored in "WHD" reception, but the fact the films seemed so similar (unlike say last year's "Mirror, Mirror" and "Snow White and the Huntsman") will be a big warning to studios moving forward duplicate projects in the future.  "WHD" is also appears to be Sony's second pricey bomb of the summer following "After Earth" earlier this month.  The studio will look to "Grown Ups 2," "Smurfs 2" and "Elysium" to save their summer season.

Dropping to fifth was Warner Bros.' "Man of Steel." The Superman reboot found another $20.8 million for $248.6 million to date. "Man of Steel" won't come close to beating "Iron Man 3" for the summer box office title, but it's certainly a much bigger hit than its predecessor "Superman Returns" ($200 million) or the Batman reboot "Batman Begins" ($205 million).

It's worth noting that "Now You See Me" solidified it's title as "sleeper of the summer" as it crossed the $100 million mark with $104.6 million.

New releases for the July 4th holiday week include the aforementioned "Despicable Me 2," the concert film "Kevin Hart: Let Me Explain" and Walt Disney's "The Lone Ranger." All three hit theaters on July 5.

Box office actuals are released on Monday.