Werepig

Werepigs are actually normal Pigs that have been transformed into monsters. Like most Monsters they are hostile and will attack anything nearby (including other Pigs). Werepigs will stop to eat any Food on the ground, and will produce Manure if they eat Vegetables or Fruits. Unlike normal Pigs they will also eat raw Mandrakes. Werepigs take two blasts from the Ice Staff to be frozen. When killed they drop 2 Meat and 1 Pig Skin.

Behavior
Pigs will transform into Werepigs if caught outside at night when there is a Full Moon (indicated by the small moon icon that appears at night near the clock in the upper-right corner). They can also be forced to transform at other times by feeding them 4 Monster Meat (they can also transform if they eat dropped Monster Meat). Once transformed Werepigs will seek out any nearby food and eat it; if no food is located they will attack nearby creatures (or characters). The next morning they will revert to their normal Pig form like nothing happened.

Hunting
The only way to find a Werepig anytime other than a full moon is to feed a normal Pig 4 pieces of Monster Meat or Durian. The Pig will immediately transform and become hostile unless there is food nearby. They are not picky and will attack the closest target to them. They have been known to attack Spiders, Hounds, Tallbirds and even non-transformed Pigs. Werepigs are very fast and can easily catch Wilson, making them difficult to escape.

An easy way to farm werepigs is to give a pig 4 Monster Meat (it is recommended to bring the pig away from any other pigs so they don't go aggro on you) and start hitting him with a melee weapon as soon as he starts transforming. Usually he will die near or at the end of the animation.

Werepigs can be put to sleep by Sleep Darts or the Pan Flute, making them easy targets. Werepigs will always stop to eat food, even when chasing something, which makes it easy to distract and kill them if you can't put them to sleep.

Trivia

 * A Werepig can be used to convert Petals to Manure as it will eat a full stack in a row without chasing anything.
 * A Werepig will retain any hat item given to them before transformation. If killed, it will drop that item, similar to a Pig.

Known Bugs

 * If a Werepig starts following a bugged food item in the ocean, it will lose interest in anything else unless it is  attacked, and the Werepig will go back to following the food item as soon as the attack is cancelled.
 * If you strike a Werepig with normal Pigs nearby, and it has not attacked any of those normal Pigs, the normal Pigs may attack you for attacking the Werepig.