In 1966, Timothy Leary was a former Harvard professor who wanted a slogan to promote the wonders of LSD. Media guru Marshall McLuhan told him the key was coming up with a catchy slogan. McLuhan suggested this, based on a Pepsi ad:
Lysergic acid hits the spot
Forty billion neurons, that's a lot.
Leary went home and tried to come up with something better. He made a list of the most popular revolutionary American slogans, including, "Give me liberty or give me death," :The only thing we have to fear is fear itself" and "A nation cannot exist half slave and half free."
Later, in the shower (where else??), the answer came to him:
Turn on, tune in, drop out.
It caught on and influenced a generation.