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!
- A Day in the Limelight: Billy's first focus episode after voluntarily stepping down as a ranger.
- Adaptational Nationality: Bara Vanish was an average Monster of the Week that was loyally serving the Machine Empire. Here, the Hydro Contaminators are an entire race onto themselves that threaten the ecosystem of an entire planet. The one we meet apparently has never even heard of the Machine Empire before given his confusion about seeing the Cogs aiding him.
- Badass Normal: Lt. Stone stumbles upon Goldar and Rito and, thinking there's an invasion afoot, chases them all over the park to try to arrest them. Granted, the two are amnesic and not up to no good, but Stone doesn't know that.
- Blind Without 'Em: Billy's vision is near-blank after losing his contacts. Thankfully, he had a pair of his old glasses stashed away just in case.
- Bittersweet Ending: The Hydro Contaminator is destroyed, but Billy has to depart for Aquitar in order to help Cestro's people deal with the larger threat that the Contaminators possess. His friends dont even get the chance to send him off, leaving them crestfallen.
- The Bus Came Back: Cestro of the Aquitian Rangers returns for this episode. Mr. Caplan also returns after last being seen in The Sound of Dischordia in Mighty Morphin' Season Three.
- Composite Character: The Hydro Contaminators' Ohranger counterpart was two separate entities.
- Nice Job Breaking It, Hero!: Cestro's pat on the back causes Billy's contacts to go flying out of his sockets and then Alpha ends up accidentally crushing them with his foot.
- Never Got to Say Goodbye: Tommy and the others miss Billy's departure by a few seconds and are somewhat depressed at the end.
- Non-Action Guy: Cestro does not morph in this episode and when he volunteers to go fight, Tommy shoots him down by saying he is needed to help Billy finish his device.
- Put on a Bus: Billy heads to Aquitar with Cestro to help them in their conflict with the Hydro Contaminators.
- Recognition Failure: Bulk and Skull do not remember Cestro despite meeting him during the Alien Rangers saga, though its justified due to no one besides the Rangers retaining their memories of the world while it was under the Orb of Doom's effects. Seemingly the case with Cestro seeing Goldar and Rito just loitering around with Bulk and Skull, as he does not react to them nor does he inform the Earth rangers about it.
- Unusually Uninteresting Sight: Despite having fought with them a couple of times during the Alien Rangers saga, Cestro does not react to seeing Goldar and Rito with Bulk and Skull nor does he inform the Zeo Rangers.
- Wham Episode: Billy graduates from High School early and in the end has to leave to help Cestro and the other Aquitians deal with the Hydro Contaminators.