The Untitled Ivan Reitman Movie, also known as Friends With Benefits, began production in Los Angeles on Thursday. The movie, originally entitled F*ckbuddies, stars Natalie Portman and Ashton Kutcher, as two people in a no-strings-attached relationship that is threatened when they begin to develop true romantic feelings for one another. The movie also stars Olivia Thirlby, Greta Gerwig, Kevin Kline, Ophelia Lovibond, and Ben Lawson. Thirlby plays Portman’s sister, Gerwig plays Portman’s brainy friend, and Kline plays Kutcher’s actor father. The movie tentatively has a January 7th 2011 release date.