In English, the plural of ninja can be either unchanged as ninja, reflecting the Japanese language's lack of grammatical number, or the regular English plural ninjas. Historical ...
http://en.wikipedia.org/wiki/Ninja

Pirates versus Ninjas (or vice versa) is an internet meme that circulates in the form of an ongoing debate that asks the question "Who would win in a fight: pirates or ninjas?
http://en.wikipedia.org/wiki/Pirates_versus_Ninjas

The Official Ninja Webpage. Real Ultimate Power. Hi, this site is all about ninjas, REAL NINJAS. This site is awesome. My name is Robert and I can't stop thinking about ...
http://www.realultimatepower.net/index4.htm

Are you ready to get pumped? Click "Yes" if yes. Click "No" if you're a little baby. YES no
http://www.realultimatepower.net/

Ninjas are legendary warriors from 14th-century Japan who were trained martial artists and were hired to do covert missions such as assassination and sabotage.
http://ninjas.com