Ain't It Funny Is A Song By American Singer Jennifer Lopez From Her Second Studio Album J.Lo 2001 . Written By Lopez And Cory Rooney And Produced By Rooney And Dan Shea It Was Released As The Album's Third International Single In Mid-2001. There Was A Very Successful Remix To The Song Which Reached Number 1 On The Billboard Hot 100 In 2001 Named Ain't It Funny Murder Remix