Types

To create a different type of NPC (besides human), just use the --type flag.

/npc create 'npc name' --type pig -b

This would make a baby pig. Leave off the -b to create an adult.

To change the type of an existing NPC, use

/npc type pig

You can use any Spigot entity type: https://hub.spigotmc.org/javadocs/spigot/org/bukkit/entity/EntityType.html