When the Diffys find a caveman who stowed away in their time machine, they name him Curtis and make him a part of the family. But after he attack Phil's teacher, Lloyd decides he must go. After all, the Diffys can't let anyone find out that they're from the year 2121! Plus, when southern belle Marla is captivated by Phil's natural charm, he uses a futuristic DNA scrambler to make himself look deformed. But it's going to take more than a transformation into a hideous beast to turn Marla away!