The Volcanic Venture

"The Volcanic Venture" or "Sonic vs A Monster from Underground" (Sonikku tai Chiteikaijū (ソニック対地底怪獣?)) is the 48th episode of Sonic X

Plot
Traveling around on the island, Eggman plans to set off the hotspot with an explosion. While Sonic, Knuckles, and Rouge investigate the subterranean landscape of the island, the others are trying to locate Dr. Eggman. Unwittingly, the intruders awaken a giant Mogera-esque robot that attacks them. Over the course of a pitched battle, Decoe and Bocoe reject Dr. Eggman and try to help, but are sent flying. Sonic then throws Eggman's explosive into the robot, causing it to explode. The island begins to sink, and everyone escapes. Decoe and Bocoe then emerge, having been rebuilt by Tails and Chuck, and denounce Dr. Eggman.