The Secret of Monkey Island was something that was unknown to possibly all of the Caribbeans inhabitants.
There are a number of theories as to what it could be.
Giant Monkey HeadEdit
The Giant Monkey Head probably belonged to some extinct form of giant monkey.
Inside it was an enormous maze through the fires of hell.
Three Headed MonkeyEdit
The Voodoo Storm that can only be passed through by creating a strange soup thingEdit
The other world mentioned is possibly the Carnival of the Damned that Guybrush was trapped in at the end of the game. However, the Carnival is known to be a construct of LeChucks, who admitted that he himself does not know the Secret.
It is unlikely that Big Whoop is the fabled secret. For one it is located on Dinky Island and secondly LeChuck is aware of its powers and mysteries.
Underground Tunnels Connecting Every Island in the CaribbeanEdit
The tunnels in which Big Whoop were hidden may have been connected to the Secret.
A Giant Monkey RobotEdit
The Giant Monkey Head was revealed to be a giant robot. However, in SoMI the giant monkey was clearly biological with a spine. It is possible that the robot was constructed along with the Theme Park.
- In Flight_of_the_Amazon_Queen a joke is made that the real secret of Monkey Island is that "Elaine is really a guy.".