Ever since a year ago, several pirate crews defeated by Z ended up shipwrecking on Dock Island. Every time this happened, though Mobston fixed their ships, the crews ended up leaving their weapons and equipment behind and quitting their journey, their resolve and dreams crushed. Mobston picked up the discarded gear and stored it in his docks, intending to give it to someone brave enough to defeat Z.
One Piece Film: Z
Following the Straw Hat Pirates' first encounter with the Neo Marines, the Thousand Sunny was heavily damaged by the White Tiger and Z's attacks, forcing the crew to stop at Dock Island. There, Mobston and his grandchildren help Franky in repairing the Thousand Sunny, and tell them everything they know about Z. Mobston also offers them to give them the gear he has stored over the year. The Straw Hats (Sans Franky) then decide to go to Secon Island, to defeat Z and get Ain to return Nami, Robin, Chopper and Brook to their normal ages.
After Secon Island's destruction at the hands of Z, the Straw Hats return on the island, where they meet Kuzan. He tells them about Z's plans, and gives them an Eternal Pose leading to Piriodo. After Kuzan leaves, the Straw Hats take the gears and weapons Mobston had stored, and prepare for battle. Franky finishes repairing the Thousand Sunny, and the crew leaves to Pirodo.
Following Z's defeat, the Straw Hats return to Dock Island one last time, to return Mobston's gear to him and bid them farewell.
- One Piece Movie 12, The Straw Hat pirates refuge on Dock Island to repair the Sunny, before the final fight with Z.