Flubber

Robin Williams

Professor Philip Brainard

Marcia Gay Harden

Dr. Sara Jean Reynolds

Christopher McDonald

Wilson Croft

Raymond J. Barry

Chester Hoenicker

Clancy Brown

Smith

Nancy Olson

Secretary at Ford Motor Company

Ted Levine

Wesson

Wil Wheaton

Bennett Hoenicker

Edie McClurg

Martha George

Jodi Benson

Weebo (voice)

Leslie Stefanson

Sylvia

Malcolm Brownson

Father