 Sound designer Andrew M. Somers (qv) created the sound of Flubber  by using a rubber balloon filled with water, Metamucil, and air. The  Metamucil became "gloopy" and in the balloon, it helped make a  rubbery, gurgly sound. The voice of Flubber was performed by  Scott Martin Gershin (qv), and was processed to raise the pitch to  sound small and squeaky.