Passive AI

Passive AI is an AI type followed by all friendly NPCs and some critters. Goldfish is only in the passive AI type if it is raining.

Behavior
An NPC with the Passive AI exhibits the following behavior:
 * Jumps over holes
 * Walks
 * Suffers from knockback
 * Can be damaged by lava
 * Cannot be damaged by the player, if it is a friendly NPC.
 * The Guide and the Clothier are exempt from this if the Guide Voodoo Doll or Clothier Voodoo Doll is equipped, respectively. Rotten Eggs are another exception to this rule.