Wilbur (Jerry Lewis) and Eliza (Madeline Kahn) Swain are the wealthy parents of twins who are enormous and extremely ugly. The twins are so hideous that their parents try and keep them hidden away from the local community. What the parents do not realise is that the twins are super-intelligent aliens who have been sent to help earth solve its many problems. However, there is just one hitch to the plan: the twins super-powers only work when they are together. When they find themselves being pursued by U.S. agents they have to be careful not to be separated - will they survive and save the earth?