WITH THE VOICES OF : Steve Buscemi ( Scamper ) , John Cleese ( Dr. Glickenstein ) , Jennifer Coolidge ( Jaclyn ) , John Cusack ( Igor ) , Arsenio Hall ( Carl Cristall ) , Sean Hayes ( Brain ) , Eddie Izzard ( Dr. Schadenfreude ) , Jay Leno ( King Malbert ) , James Lipton ( himself ) , Molly Shannon ( Eva ) and Christian Slater ( Dr. Schadenfreude 's Igor ) .