 As revealed in "The War for Dimension X", before the events of the show, they were once all the peaceful race known as the Utroms, until one of them, a female scientist named Kraang (voiced by Roseanne Barr in seasons 1 and 2, Rachel Butera in season 3), discovered the mutagen, which is milked from giant native worms called Kraathatrogons, and used it to enlarge herself while gaining psychic powers.Becoming deranged, she renamed herself Kraang Prime and used her power to subjugate most of her species by copying her mind into theirs.These affected Utrom came to be known as the Kraang as they and Kraang Sub-Prime (voiced by Gilbert Gottfried), an Utrom who willingly swore loyalty to Kraang Prime, work to infiltrate and mutate other worlds.