A moonraker
A moonraker is a failure who dreams big but can't even make it out of their own stupid head. They’re like a kid who says they’ll be president but forgets to do their homework.
My cousin thinks he’ll be a rock star, but he can't even tune his guitar.
My neighbor says he’ll win the lottery, but he still eats cereal for dinner.
My dog tried to catch the moon, and now he’s stuck in the yard.