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. Presumably he also studied the last known movements of the S.S. Minnow, as he claimed to be the only survivor and that his wife and the five other passengers were lost at sea in order to bolster his fraud. 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. He also considers selling Howell Industries to Consolidated Industries, but it took considerable time for such a merger to go through, so he waits it out with more partying. 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. In order to avoid being exposed, he knocks out Mr. Howell and steals his identity by switching their clothes, confusing Mrs. Howell, the Skipper and Gilligan in the process. When a news flash says that the fake Mr. Howell has been outed as an imposter when his signatures were checked against documents the real Mr. Howell signed years ago, 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.