An Enemy in Need

"An Enemy in Need" or "Dr. Eggman Appears!" (Dr.エッグマン参戦！) is the 56th episode of Sonic X

Plot
After saving the planet in the former episode, Sonic and his friends are thanked in a feast. Dr. Eggman is watching the scene and he thinks about his next scheme to take away the Chaos emerald. Bokkun suggests a plan to Eggman, but the evil doctor doesn't notice that it has been elaborated by Rouge, who made her way to the Egg Carrier. Eggman soon finds Knuckles and he tries to persuade him that he didn't want to be a bad person anymore, and he wishes to leave the planet by using a Chaos Emerald. Knuckles believes him and he finds the others in order to take the Emerald they just found and to give it to Eggman. Sonic disagrees and both of them engage in a fight. Taking advantage of the situation, Eggman almost takes the Emerald, but he is stopped by Amy and the others. This gives a Chance for Rouge to steal the Chaos Emerald, But at the same moment, a frog-shaped Metarex rises from the ground and it grabs the Emerald. Eggman let Cosmo go and he engages a fight against the Metarex. However, Eggman is defeated. It's Sonic's turn to fight the Metarex and, with the help of the Sonic Power Cannon and a Chris' trick, the blue hedgehog is victorious. The episode ends as Knuckles apologizes for being fooled by Eggman.

Trivia

 * When Amy explains how Eggman tricked Knuckles, his eyes are green for the moment,instead of Purple.