Zelkova Strikes Back

"Zelkova Strikes Back" (メタレックスの正体！？) is the seventy-second episode of the anime series, Sonic X. It first aired on 12 April 2005 and 18 March 2006 in France and United States respectively.

Japanese version

 * "SONIC DRIVE" - Opening theme
 * "The Shining Road" - Closing theme

English version

 * "Gotta Go Fast" - Opening theme (USA and CAN)
 * "Sonic X" - Opening theme (AUS, NZ and UK)
 * "Gotta Go Fast" (shortened) - Closing theme

Plot
The Blue Typhoon arrives at a planet, but Yellow Zelkova attacks the Blue Typhoon and forces it to crash onto the molten surface. Zelkova is equipped with a special energy shield that was built by Dr. Eggman, whom he praises before telling a riddle for Sonic's friends to solve "What is the place we are scared to go at night, but we rest in peace?"

After solving the riddle by answering a cemetery, Zelkova told them that he will take the opportunity to teach Sonic's friends that the molten planet will become their grave by beginning to punch their ship towards the edge of the cliff down into a collecting lake of lava below. Sonic attempts to stop him, but is unable to break through the shield. Picking up where they left off, Zelkova and Knuckles get into a fierce battle, during which Knuckles smashes Zelkova's knee and breaks the spikes on one of his gloves. Using a cable from the Blue Typhoon, Sonic and the others channel lightning to overload Zelkova's shield. Zelkova's mechanical outer body is destroyed, revealing his flesh form beneath. Zelkova attacks, but is knocked into a nearby lava pit by Knuckles.

Pale Bayleaf informs Eggman of Zelkova's demise, mocking the failure of his shield. Shadow and Rouge find a fake Chaos Emerald at the top of the tree, but they hear groaning from its base. They find Leon (from the Resistance in Episode 68) being consumed by the tree, saying that the Metarex betrayed them. He also gives Shadow a memory chip and says it's not too late to destroy the Metarex before succumbing to the effects and dying shortly afterwards.

Trivia

 * There is an extra scene in the Japanese version, where Knuckles tries to help Yellow Zelkova from a lava pit, but Yellow Zelkova refuses his mercy and he accepts his death which can be traced back to how Sonic tried to save Hyper Metal Sonic in Sonic OVA in a similar scenario.
 * (Japanese version only) When Sonic and Knuckles are fighting Yellow Zelkova, the Radical Highway theme song from Sonic Adventure 2 called "Vengeance is Mine" plays.
 * This episode shows that Sonic is able to move as fast as (if not, faster than) the speed of light since Sonic can keep himself ahead of the lightning he gathered to attack Yellow Zelkova and lightning obviously travels at the speed of light.
 * When the episode first aired in the US, Yellow Zelkova is sliding into the lava, in second airing he disappears in a gleam of light. Also at the ending where Shadow and Rouge found Leon engulf into a tree, camera pans away and see the other members of the resistance same fate, the second airing edit out the members to fully grown trees.