Role in the series
Gear Island first appeared in the episode "The Island of Doctor Undergear", after successfully stopping the lava from Belch Mountain,Captain Gizmo's golden gear that powers him is damage leaving Jake and his crew with the task of repairing there mechanical matey,when they uncover a map inside Gizmo leading to Gear Island in hopes of finding someone who can help Captain Gizmo. Once on the mechanical island Jake and his crew are captured by the mechanical wildlife and brought to face their creator, the evil pirate mad scientist Doctor Undergear, who wasn't please to see Jake and his crew on his island until Doctor Undergear spots his old missing minion Gizmo much to the shock of Jake and his crew. Seeing that Gizmo had the wrong gear and replace it with a purple gear making Gizmo evil once more. But Jake and his crew soon put a stop Doctor Undergear plot and return Gizmo back to his kind self and destroyed the purple gear preventing Doctor Undergear using it before returning to Pirate Island. Doctor Undergear swears he'll have his revenge on the young pirate team.
Gear Island makes a reappears at the end of the episode "Shark Attack!", Undergear returns to his lair using after being defeated by Jake and his crew for the second time using a balloon. But before Undergear could set foot back on his island he accidentally pops the balloon as he curses Jake and his crew sending him plummeting into the Never Sea where he is chased back to shore by two hungry Never-Sharks.
Gear Island makes a brief reappears in the episode "The Legion of Pirate Villains!", Undergear was fixing his latest inventions when he is captured by the Grim Buccaneer to join his Legion of Pirate Villains to find Captain Colossus's legendary treasure hidden on Colossus Island.
Gear Island reappears in the episode "Crabageddon!", Doctor Undergear need more space for his creations and decides to takeover King Crab Island as his new lair. During his hostile takeover of Crab Island, Undergear with the aid of his Crab Bots capture the Crab Pirates and King Crab's son Crab Louie. King Crab attempt to stop Undergear himself but was quickly defeated by the mad doctor. King Crab soon recruits the aid of Jake and his crew to put a stop to Doctor Undergear wicked scheme.