Who said "I've learned that sometimes you have to howl at the moon."?

This quote is attributed to Snoopy.

I've learned that sometimes you have to howl at the moon. - Snoopy

"I've learned that sometimes you have to howl at the moon."

Snoopy Freedom

"I think I'm dying. Send for a doctor immediately!"

"Rats! Another day, another disappointment."

"Sometimes I lie awake at night and ask, 'Is life a multiple choice test or an essay?' Then a dog barks and I realize it doesn't matter."

"I love mankind. It's people I can't stand."

"Freedom to pursue your passion is precious."

"Freedom comes at a cost."

"Order isn't restriction. It's freedom."

"Freedom comes with responsibility"