One piece: Chinjou shima no chopper oukoku (2002) More at IMDbPro »

Takes place after the events from the Drum Island episodes.

Chopper is the newest crew member of the Straw Hat Pirates. Only he soon finds being a pirate to be a bit frightening after hearing the dangers of the sea. The crew is about to head for Crown Island. Which has a barrier of geysers that form a crown. The Going Merry ship got caught in the geysers. And was sent flying over the island. Chopper fell off the ship and landed in the middle of the island below. He was greeted by a group of talking animals & a jungle boy named Momambi(An obvious Jungle Book parody).

They believe Chopper is their new king, as legend has it that a new king comes from the heavens when the old one pasts away. Soon Chopper will find it hard to convince the locals that he's not eligible to be a king. But Momambi insists Chopper to stay with them as their leader. Meanwhile Luffy and the others search for their lost reindeer doctor. Only to find out that a group of human hunters have been terrorizing the island. Lead by a horn eating/violin playing Count Butler. Associated with General Hotdog & President Snake. Count Butler plans to eat the island's sacred crown so he can obtain immense powers. Will Luffy be able to stop the Count? Will Chopper be able to ditch his role as king? And not to mention Zoro wanting to fight General Hotdog to prove who's stronger. And Sanji getting even with President Snake to see who's better.

This is in fact a spin-off rather than a sequel. Since Vivi & Carue are absent in this one. It's like seeing an alternate retelling of the Straw Hat Pirates' journey. The main character's clothing is different. Specially when Luffy's shirt has a #1 on it.

The good thing about it is the use of abstract animals(who are much different than the kind you'd see from the Gaimon episode). The secondary & minor character designs. And there's never a dull moment, much like the time pace you'd see in the previous films.

It's a must see for the Tony T. Chopper fans. As he's the main subject of this spin-off. And again very easy to find in fan subs.