Cestro

Cestro, is the Blue Aquitar Ranger of the Aquitar Rangers. He is an Aquitian that requires waters of Aquitar in order to live.

He is also referred to as Blue Alien Ranger on Earth, as well as Mighty Morphin Alien Blue Ranger

Biography
Like his Mighty Morphin counterpart, Billy Cranston, Cestro is a technological genius. When Billy successfully managed to restore his own age by means of the Power Coins before they were destroyed, he and Cestro frequently worked together to find a similar cure for the other Rangers - as well as finding a means to keep the Aquitians hydrated with pure water. In this way, Cestro was the Alien Ranger who received most attention in storylines (alongside Delphine, the team leader).

Cestro had a guest appearance in Power Rangers: Zeo, in which he came to Earth again, seeking Billy's help to fight off a menace on Aquitar called the hydro-contaminators. Billy's trip to Aquitar saw the beginning of the story arc in which he was permanently written out of the show. Indeed, the Aquitian that Billy falls in love with on Aquitar, Cestria, is believed by some to be Cestro's sister or similar relative (though others dispute this because of the different races of the actors playing the two characters).

In Space
During the invasion of the universe by Dark Specter's United Alliance of Evil, Cestro and the other Aquitian Rangers battled Divatox's army on Gratha, where they were defeated. They were later saved by Zordon's Energy Wave.

Trivia

 * Cestro is the first male Blue Ranger to have a light blue costume (next was Shark Spirit Ranger).
 * He is the only Ranger with a light blue costume to not have water-based powers, but he does live on a water planet.
 * Of all the Alien Rangers, Cestro has made the most return appearances.