No Strings Attached (2011)

Director: 

Ivan Reitman

Writers: 

Elizabeth Meriwether (screenplay), Michael Samonek (story)

Stars:

 Natalie Portman, Ashton Kutcher and Kevin Kline

Genre:  Comedy | Romance

Plot:

A guy and girl try to keep their relationship strictly physical, but it's not long before they learn that they want something more.