Gilligan discovers some ancient stone tablets that the Professor thinks may contain the secret of getting them off the island. That night, Gilligan dreams that he is a caveman chiseling a story on a stone tablet three million years ago.
Mary Ann falls backwards while watching Ginger perform on stage, and, when she awakens, she thinks that she is Ginger. Meanwhile, Gilligan accidentally watches as the Professor attempts to hypnotize Mary Ann, and thus he begins to think that he is Mary Ann.
Gilligan and the Skipper find an ancient Kupaki totem pole which is topped with a head that looks just like Gilligan. When fierce Kupaki headhunters come to the island, Gilligan must convince them that he is their ""mashuka"" or sacred ancestor.
Lightning strikes Gilligan during Skipper and Gilligan's bowling tournament, and his stone bowling ball becomes molecularly attached to him. The Professor tries to help Gilligan, but ends up causing him to become invisible.
An loin-cloth clad ape-man (Tongo) comes to the island, and makes off with their food and supplies. Actually, he is an out of work actor, who tries to convince the Castaways that he is a real uncivilized ape-man while studying for an upcoming role. After he cowers when confronted by a ""real"" gorilla, he leaves the island and the Castaways behind.
Mrs. Howell starts receiving mysterious love notes, and the source remains a mystery until Mr. Howell is caught in the act. Mrs. Howell dreams that she is Cinderella, and Gilligan is her fairy godfather. The Professor rigs up a lie detector using the ship's horn and batteries from the radio.
Gilligan is made a deputy sheriff, and begins to take his job too seriously. He ends up locking everyone up in a make-shift jail, including himself! Of course, while the castaways are locked up tight, another potential rescue plane flies over the island.
One by one, all of the Castaways mysteriously disappear. Gilligan then dreams that he is Dr. Jekyll and Mr. Hyde. In the end, Gilligan rescues them from the hidden World War II munitions pit that they have all fallen into.
A mad scientist lands on the island, and makes the castaways work for him through the use of rings that, when placed on their fingers, cause them to fall under a hypnotic trance. What are his evil plans? To use the hypnotized castaways to rob Fort Knox!
Famous Hollywood director Herald Hecuba lands on the island during his world-wide talent search. The castaways put on a musical version of Hamlet in order to impress the director, with hopes that he will take them back to Hollywood when he leaves.
Gilligan finds a crate of radioactive vegetable seeds. The plants grow quickly and grossly misshapen, but the Castaways are so hungry for new items in their diet that they consume them quickly. The plants, when eaten, give the castaways super-human powers. Of course, after he realizes that the vegetables are radioactive, the Professor saves the day by making a homemade soup to absorb the radioactivity.