The turtles are named after famous artists from the Renaissance period. Their names are Leonardo, Raphael, Donatello, and Michelangelo. They live underground in a sewer under Manhattan, and try to keep themselves hidden from people mankind in general, fearing humanity would never understand. While helping their friends, they often end up in trouble fighting crime and villan. Their enemies may vary from inner town street gangs to extraterrestrials. There are a few humans who know about them, a woman named April O'Neil and a man named Casey Jones, and some other people, depending on version. Some versions also use Casey Jones' grandmother's farmhouse in Northampton in Massachussetts as a hangout for the turtles.