William "Billy" Cranston is the first Blue Ranger of the Mighty Morphin Power Rangers in the 'modern era', during "Switching Places", Billy accidentally switch bodies with Kimberly Ann Hart becoming (temporary) the Pink Ranger, he later became the first Blue Ninja Ranger of the Ninja Rangers.
Retroactively, he is also referred to as the Mighty Morphin Blue Ranger or Blue Mighty Morphin Ranger, though these are terms of address referencing the show as opposed to proper labels.
During Power Rangers Zeo, Billy served as the technical expert helping from the Power Chamber the Zeo Rangers against the Machine Empire, he leaves Earth to spend time with his girlfriend, living now on Aquitar with Cestria.
Until his departure, he was considered the brains of the Power Rangers team, creating many gadgets with which to solve problems that not even Zordon foresaw, and even invented the first team's wrist-worn communication devices (it is believed, though not proven, that he created every other communicator up until his departure from the show).
Many years later, during the events of Power Rangers Beast Morphers Season 2, Billy responded to his old teammate Jason's signal and forms part of the Legendary Dino Rangers army against Goldar Maximus and his Army of Foot Soldiers.
Two years later, Billy tried to bring back Zordon but unintentionally brought back Rita Repulsa who gained a robotic body after taking over Alpha 8’s body. Billy followed Rita and ended up fighting her and a gang of Putty Patrollers, eventually he sent a distress call which was answered by his former Team but the fight ended in tragedy when Trini Kwan was killed by Rita.
One year later, on the anniversary of Trini’s death, Rita returned and captured Jason Lee Scott, Kimberly Hart, and Tommy Oliver. Billy was able to escape capture along with Zack Taylor and Trini’s daughter, Minh. Back at the new Command Center, Alpha 9 activated Bandora Protocol, and with the help of Zack, Minh (who had become to new Yellow Ranger,) Rocky DeSantos and Kat Hillard, Billy was able to fix his past mistake and avenge his fallen friend.
Months later, Billy joined the Dino Fury Rangers to fight the new threat of his old enemy, Lord Zedd, and his alliance with Squid Ink Inc., who sought to eradicate good from the universe. Billy assists Solon in mentorship responsibilities for the Rangers, who became the Cosmic Fury Rangers, and along with several Rangers, Billy helped the team eliminate the enemy fleet. After their victory, Billy learned from Aiyon that he had encountered Zordon, which affirms his resolve.
