A Large, flat, pink rubber coin used as galactic currency. As described by Douglas Adams in 'The Resteraunt at the end of the Universe'
"The exchange rate of 8 Ningys to one Galactic PU is simple enough. However, since a Ningy is a triangular rubber-coin ,6800 miles along each side, no one has ever collected enough to own one PU. Besides which, if you did ever own enough, you would have a great deal of trouble exchanging them, as most banks refuse to deal in small change."