Splinter

Splinter is the wise mentor and father-figure of the heroic Teenage Mutant Ninja Turtles - he is a rat who lives in the sewers along with his students and is responsible for teaching them the ways of martial arts as well as guiding them on the right path and, if necessary, dealing discipline to teach them valuable lessons.

He is often referred to as Master Splinter by the turtles, who are as loyal to him as children and indeed see him as a father-figure - he in turn treats them as his own sons and is a gentle but firm teacher who is not above fighting himself if he feels his family is in danger.