Please make a plugin as this mod http://www.minecraftforum.net/topic/472937-181castle-defendersv202-updated/
This is a mod. Bukkit is for plug-ins. Use CitiZens with the type "Guard" and set them as a bouncer. Click PS: You don't have to use every type of npcs. Only drag&drop the type.jar into the types-file, which is auto-generated on startup. GC
