William "Billy" Cranston is a fictional character in the
Power Rangers universe. He is the Blue Ranger in the series
Mighty Morphin Power Rangers, and was portrayed by actor
David Yost. Billy is the only original Power Ranger to remain for the entire
MMPR series, and is the second longest-serving Ranger overall behind
Tommy Oliver. 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 he even invented the first team's wrist-worn communication devices.