“If you're referring to yourself as a 'grown-up', then you're still totally a kid. 'Grown ups' call themselves adults”
“You're dead if you aim only for kids. Adults are only kids grown up, anyway”
“Adults are only kids grown up”
“Until you're grown-up they send you to reform school. After you're grown-up they send you to the penitentiary.”
“When you're old enough to write a book for children, by then you'll have become a grown up and have lost all your jokeyness. Unless you're an undeveloped adult and still have an enormous amount of childishness in you.”
“The problem with growing up is that once you're grown up, the people who aren't grown up aren't fun anymore.”