The phrase "purple cow" means something that stands out and is unusual or remarkable. It represents something unique or extraordinary that catches people's attention and makes them remember it. Full definition
Click on image to enlarge etc.] Seth Godin and I will be there, signing more Purple Cow prints. (gapingvoid.com)
We reference Seth Godin's Purple Cow in a discussion of how to go about honing your message and spreading the word to stand out and create buzz. (good2bsocial.com)