I found some by Paul Graham, of all people, when I typed in "a startup is like" into Google:

"A startup is like walking on your hands. A startup is like a pass/fail course. A startup is like a small boat in the open sea. A startup is like a mosquito. A startup is like a hang-glider launch.

No.

A startup is like being a mosquito trying to fly a hanglider-boat while waking on your hands and not failing school."

Can somebody top that (and throw in a marketing aspect?)