The Witch Doctor lives in the "Mysterious Hut" secret lot for Twikkii Island from Bon Voyage. His bathtub, television, dishwasher and microwave are broken. Once your Sim repairs them and mops up for him, he will thank the Sim that spoke to him and give them a voodoo doll. The voodoo doll can be used to affect other Sims.
Despite having the voice of an elder, he is actually an adult. If the "boolprop testingcheatsenabled true" cheat code is used, he can be summoned by way of the mailbox. However, if Bon Voyage is not installed, his mask will be white, with the text "accessory mask" and a red cross. However, it is not recommended to add him to a family.
It is possible to miss receiving the voodoo doll from the Witch Doctor if the player lets the interaction wait in the queue for too long or interrupts the interaction. When this happens, there is no way to get it unless the player re-visits the lot and repairs all of the items again.
If your Sim attempts to use the voodoo doll on the Witch Doctor, a notification pops up saying "Now you've shown your true colors. My own magic can't be used against me." This will decrease the Sim's relationship with the Witch Doctor significantly, but your Sim will not suffer any other consequences from this action.