Voir Power Rangers: Zeo - Episode 10

Billy, by way of having too many credits, graduates a year early. He's stunned by this, but plans for his future are put on hold when Cestro (the Blue Alien Ranger) returns from Aquitar, in need of Billy's expertise in devising a way to stop the Hydro Contaminators from polluting his watery homeworld. One of the Hydro Contaminators comes to Earth, joins forces with the Machine Empire, and just might prevent Billy & Cestro from returning to Aquitar to fulfill this mission. Also, Bulk & Skull are put in charge of guarding Cestro's ship while he's away, so the pair gives the task to Goldar & Rito, sending the amnesiac monsters fleeing from their assignment when Lt. Stone spots them!