Ashton Kutcher was not co-stars with Cameron Diaz.
What Happens in Vegas is a 2008 American comedy film directed by Tom Vaughan , written by Dana Fox and starring Cameron Diaz and Ashton Kutcher .. Tom Vaughan. Tom Vaughan ( director ). Dana Fox. Dana Fox. Cameron Diaz. Cameron Diaz. Ashton Kutcher. Ashton Kutcher. comedy film. comedy film. The title is based on the Las Vegas marketing catchphrase `` What happens in Vegas , stays in Vegas . ''