As one of the original teens chosen by Zordon to fight Rita, Billy became the Blue Ranger.  His speciality was in using his superior IQ to create devices to help save the Rangers and Angel Grove. Once awkward and shy, Billy has evolved over time into the confident and capable person he is today.  When Master Vile reversed time Billy assumed command, proving himself to be a capable leader.  It was during that time that the Rangers obtained their Zeo powers, with Billy making the choice to remain in the Power chamber as an advisor, communicating with them and creating weapons and Zords for them.  Later, after he began his rapid aging, he left Earth for Aquitar.