The four-day President's Day holiday weekend got off to a suprising start on Friday as Liam Neeson's "Unknown" topped expected champ "I Am Number Four" at the box office.

The Warner Bros. thriller, which successfully copied many elements of Neeson's previous hit "Taken" in its marketing campaign, found $6.7 million on Friday for what could be a $25-27 million gross over the four day frame.  "Taken" was also assisted by much better reviews than the other new debuts, "Four" and "Big Mommas House: Like Father, Like Son."

"I Am Number Four," on the other hand, grossed a lower than expected $6.2 million on Friday.  The first film from Dreamworks Studios in their new partnership with the Walt Disney Company, "Four" was expected to easily win the weekend.  The PG-13 thriller will have to count on strong matinees to make up the difference if it wants to overtake "Unknown."

Dropping from the top spot to third was the Adam Sandler and Jennifer Aniston comedy "Just Go With It" with another $5.2 million.  The Sony Pictures release has amassed $47.7 million in just eight days.  It will be intriguing to see of Sandler's fanbase can push the critically panned comedy close to the star's typical $100 million gross.

Debuting in fourth with some of the worst reviews of the year (or any year) is Martin Lawrence's return to drag, "Big Mommas House: Like Father, Like Son" with $4.8 million.  Rating only at 5% on Rotten Tomatoes (which mean two critics actually recommended it), "Big Mommas" could end up with $15-17 million by Monday.

"Gnomeo and Juliet" rounded out the top five with another $4.3 million for $35.3 million to date.  The Elton John produced family flick should have much stronger Saturday and Sunday matinee business and could find another $20-22 million by Monday.

Look for continuing box office updates throughout the weekend on HitFix.