The Impostor is an unidentified con-artist who has had plastic surgery to resemble millionaire industrialist Thurston Howell III. His real name is unknown, but he used his new face to steal Mr. Howell's identity and take over his position as CEO and chief stock-holder of Howell Industries, claiming he was the only survivor of the S.S. Minnow. Once in control of the company and its assets, he started selling off its stocks and properties for money which he spent in large amounts on female companions or gambled away at Sunnyside Racetrack. At one point, he even considers selling the company to Consolidated Industries. During a cruise in the South Pacific with thirty-nine girls on a private yacht, he is lost overboard carrying a champagne bottle and a lady's shoe. He ended up washing up on the island with the Castaways and was stunned to learn that the real Mr. Howell was still alive. For unknown reasons, he knocks out Mr. Howell and takes over his identity on the island, confusing Mrs. Howell, the Skipper and Gilligan in the process. However, after the Professor reveals that the impostor had been outed back home after a comparison of signatures, the fraudulent Mr. Howell flees the island in Mr. Howell's clothes and his real wallet in the back pocket. A subsequent radio broadcast reveals that he was arrested after being picked up in the ocean and sent to prison for twenty years.
- The Mr. Howell Impostor is of course played by Jim Backus. The visual effect of having Jim Backus play both Mr. Howell and the impostor is called "Split-Screen," whereby the same scene is filmed twice with the actor in each place at separate times. Split-Screen relies on the camera being fixed in place. Many of these techniques were repeated in Gilligan vs. Gilligan and All About Eva.
- In scenes where camera movement is required, the show employed the use of stand-ins, tight shots, obscured views and/or the use of rubber masks.