Defeat Him! The Pirate Ganzack is a One Piece OVA premiered during the 1998 Jump Super Anime Tour. It was the first crack at an anime for the series, being produced by Production I.G rather then Toei who would handle the anime from then onward.
The story is set between the Orange Town and Captain Kuro arcs of which the crew only consists of Luffy, Zoro and Nami at the time. As they're making their way across East Blue, their dinghy is suddenly attacked by a Sea King and the trio is separated. Luffy ends up washed ashore on an island where he meets a young girl in a mini-suit of armor named Medeka trying to fight some pirates. Once Luffy takes care of them for her, she explains their island has been taken over by a pirate name Ganzack who has enslaved the citizens to make a weapon for him with the intent to take over the Grand Line. Medaka coaxes Luffy to attack him since Ganzack likewise has taken near all the island's food for himself. But Ganzack naturally isn't a pushover and a tough battle ensues for our fledgling pirate crew.
- Attack of the 50-Foot Whatever: Ganzack has a Plesiosaur sea king at his disposal. Not surprisingly it's the creature that attacks the trio at the start.
- Continuity Snarl: Bit of a mistake with the dinghy. After the Orange Island arc, the three sailed away in two of them which they stole from Buggy's crew (One Nami tricked out of three of Buggy's pirates and one they got at the pier), not one singular one.
- Early-Installment Weirdness: Luffy's stretching sounds were much more realistic to that of how real rubber would be when pulled.
- Fake Defector: Nami pretends to have thrown in with Ganzack when Luffy and Zoro are captured. But naturally, she's just playing him to get his treasure and banking on Luffy and Zoro to take Ganzack out.
- Hoist by His Own Petard: Ganzack was developing a missile weapon which he could launch from his ship. He tries using it to destroy the island, only for Luffy to send Ganzack flying into the incoming missile, destroying it and finishing off Ganzack in the process.
- Off with His Head!: In the climax, Ganzack attempts to behead Luffy but gets Medeka instead who jumps in front of the swipe. Luckily she ducked her head in her armor.