'Shrek Forever After'In the biggest upset of the year so far, the ogres defeated the cougars. 'Sex and the City 2' went into Memorial Day weekend as the expected champion; instead, it may have to settle for third place as 'Shrek Forever After' remains the top ticket-seller in its second week.

Studio estimates for the four-day weekend have 'Shrek' finishing with $55.7 million, for a total of $145.5 million since it opened 11 days ago. That includes an estimated $12.4 million earned on Monday's holiday. The film's Friday-to-Sunday total is $43.3 million, down just 39 percent from last week's underwhelming opening.

Duking it out for second place are 'Sex' and fellow newcomer 'Prince of Persia: The Sands of Time.' Like 'Sex,' 'Prince' opened well below expectations, but early estimates suggest moviegoers preferred Jake Gyllenhaal's flexing pecs to 'Sex.' The four-day estimates give 'Prince' a scimitar-thin edge, with $37.8 million over $37.1 million for Sarah Jessica Parker and company. The three-day Friday-to-Sunday totals, however, had put 'Sex' ahead with $32.1 million to 'Prince's' $30.2 million. We may not have a definitive winner until final numbers are released on Tuesday.