ONE PIECE: Chinjuu-jima no Chopper Oukoku

ONE PIECE 珍獣島のチョッパー王国

The crew comes upon Crown Island where the animals can talk and they makes Chopper their new king. But there are human hunters there also looking for the legendary horns that will give the person who consumes it immense power. Luffy and friends must stop them from destroying this animal kingdom.

(Source: Anime News Network)