Why would an actor who has successfully made the transition from TV performer to movie star return to TV at the peak of his career? Ashton Kutcher, who is returning to TV as Charlie Sheen's replacement on Two and a Half Men addressed that question on David Letterman's TV show Wednesday night. He recalled the time when Robin Williams, who had recently won an Oscar, stopped by the set of That '70s Show , which co-starred Kutcher, and remarked that he missed doing Mork and Mindy. Said Kutcher "I never forgot that when I was on That '70s Show because I never forgot what we had, and how great and how fun the job was and how incredible it was, and how great it is go to work every day and make people laugh." Kutcher predicted that the ratings for Two and a Half Men are "going to go through the roof. ... I've been laughing really hard."