His plan to become a famous actor is just pie in the sky.
pie in the sky
idiomA fanciful notion; an unrealistic or ludicrous concept; the illusory promise of a desired outcome that is unlikely to happen.
Origin
first recorded 20th c.The phrase is originally from the song “The Preacher and the Slave” (1911) by Swedish-American labor activist and songwriter Joe Hill (1879–1915), which he wrote as a parody of the Salvation Army hymn “In the Sweet By-and-By” (published 1868). The song criticizes the Salvation Army for focusing on people’s salvation rather than on their material needs: : You will eat, bye and bye, : In that glorious land above the sky; : Work and pray, live on hay, : You’ll get pie in the sky when you die.
The company promised us a massive bonus, but most employees think it is just pie in the sky.
The politician’s grand promises of instant economic prosperity were dismissed by critics as nothing more than pie in the sky.