The Bender duplicates were created by Bender as a way of getting out of being assigned folding sweaters. Bender created them by using a machine created by the Professor that makes half-sized duplicates of objects. Each duplicate had the same idea and made half-sized duplicates of themselves. They are last seen leaving Earth because they don't want to have to do one quintillionth of a thing.
These Benders also also make fun of an ugly giant.