When
Fenton Crackshell shouts the words "Blathering Blatherskites!", his
metallic suit whizzes through
time and
space to transform him into GizmoDuck,
Scrooge McDuck's personal
bodyguard.
The GizmoDuck suit was created by Gyro Gearloose, who is Scrooge's inventor, genius, etc. Fenton discovered the suit by accident while working in a bean factory, and tried to use the suit to become a hero to impress his girlfriend, Gandra Dee.
GizmoDuck has been known to be assumed by at least the following people:
Launchpad McQuack
Fenton's Mother, as GizmoMama
Huey, Dewey and Louie, the nephews of Scrooge
Webby