Like all ninjas, he can't be interacted with. As a result, he can't be made playable without cheats. He has 20 personality points, instead of the usual 25. Ninja has the same facial structure as Goopy Gilscarbo.
He can easily be cloned in Create a Sim with debugging mode on. Ninja has short black hair in a buzz cut. Even though he has black hair, his natural hair colour is actually brown.
Do NOT attempt to add Ninja to a household, make him selectable, or tamper with him in any way or form. Doing so will corrupt the neighbourhood he is in.