Ashton Kutcher ( born February 7 , 1978 ) is an American actor . He became famous when he played Michael Kelso on That '70s Show . Christopher Ashton Kutcher ( ; born February 7 , 1978 ) , best known as Ashton Kutcher , is an American actor , producer , former fashion model and comedian , best known for his portrayal of Michael Kelso in the Fox sitcom That '70s Show .