What is the secret of Monkey Island?

I remember when playing each Monkey Island on release (with the exception of the Tales of Monkey Island) - and in each of the first 4 games I always remembered "knowing the secret of Monkey Island".

During the end of the first game I assumed it was the fact the undead LeChuck was hiding with the catacombs of a giant monkey head. I didn't think there was anything to suggest the secret was anything more complex or yet unexplained after finishing the first game. The game had an ending and there was nothing to suggest the story would continue after the demise of LeChuck.

When I played the second game, I had no doubts about my conclusions for the first game until the end when LeChuck reveals himself as your brother (and everything in the two games was a fabrication). I remember still thinking that the secret was the way LeChuck was hiding on the island - but because now everything before wasn't real it didn't matter what the secret was. When talking to others after playing the second game some believed the real secret was actually Big Whoop (although I didn't come to the same conclusion).

The Curse of Monkey Island made an arguably weak explanation of events between the second game and the start of the third game. However, everything previous was thrown out when Guybrush asks LeChuck for the secret of Monkey Island - as if the secret was in fact never explained before.

The fourth game is explicit in that the monkey kombat is the real secret.

Remember, by the time the first three games were released the internet was not like we know it today. It seems to me that the on-going notion of the secret never being explained has become a running joke fuelled by online debates, when in fact there was no problem during the first 2 games.

Conclusion

The secret was the fact an undead LeChuck was hiding under the monkey head (implied).

This then changed during the series to the fact the giant monkey head was part of a robot (explicit).

The asking of "what is the secret of Monkey Island" became a running joke perhaps from the third game, and continues beyond the fourth game (despite the explicit revelation).

The secret of Monkey Island seems to be massive Voodoo powers, including Eternal Life. Or rather, Eternal Death.

• Secret of Monkey Island - LeChuck went to find the secret and came back as a ghost.
• LeChuck's Revenge - LeChuck was resurrected by Largo LeGrande using an offscreen Voodoo ritual of some sort. LeChuck clearly has Voodoo powers during the game. At the end of the game, it's implied that he has locked Guybrush into some sort of hallucination or just outright cursed.

Unfortunately, being the only two games Ron Gilbert was involved with meant that the story started to veer off course a bit:

• When Jonathan Ackley and Larry Ahern wrote Curse of Monkey Island, they kept the Eternal Death theme going, but dropped the Voodoo powers bit. They also added a giant carnival to try to explain the ending of LeChuck's Revenge
• Escape From Monkey Island outright ignored canon and made the secret the giant Monkey Robot below the island (which was clearly not there in the first game)

Tales From Monkey Island went back to the "LeChuck has Voodoo Powers" bit. This shouldn't be a surprise as Ron Gilbert was involved in the production of this game.

One key point late in the game was that LeChuck existed in both the world of the living and world of the dead at the same time.

It was also implied that LeChuck's power (the secret of Monkey Island from the first game) can be transferred to other people. This started with The Pox of LeChuck and the after-credits scene at the end of Tales.

In my opinion, the secrets of monkey combat and The Ultimate Insult can be considered the secrets of Monkey Island as they are supposed to enable a pirate to effectively defeat any other pirate. This fact isn't mentioned directly in any of the games, but considering the fact that ever since Monkey Island 1, you have to use your wits in combat and defeat your opponents using insults, I think it is fairly plausible.

Short answer:

Currently, almost nobody knows what the original secret was. By "original" I mean the secret mentioned by the characters of MI1. The person who wrote the original story for MI1 and MI2, Ron Gilbert, has never explicitly revealed it in the games or publicly.

The writers of the three subsequent games in the franchise (MI3, MI4, Tales of MI) didn't know what the original idea was.

At the time of writing, Ron Gilbert is developing a sixth game, "Return to Monkey Island", expected for 2022. It's possible that the original secret will be finally disclosed after 32 years.

Some clarity about the original secret:

Any fan "theory" should take into consideration that several game characters in MI1 have the notion that the secret of Monkey Island is something related to the island itself.

Also, the secret existed well before LeChuck (still alive) went to Monkey Island. Actually, LeChuck goes there to discover what the secret of the island is.

Here is a list of characters in MI1 who either go to Monkey Island to find its secret or who mention that the island has a secret:

Estevan: "LeChuck was a fearsome pirate. He tried to impress the Governor by sailing off to find the Secret of Monkey Island™."

Stan: "You see, two previous owners of this ship were two adventurous pirates. They set off, like many before, to find the legendary Secret of Monkey Island™."

The Captain of the Sea Monkey (in the logbook): "Toothrot and I filled the rowboat with supplies and are ready to set out to Monkey Island™. We are both excited at the prospect of being the first civilized people to learn the Secret of Monkey Island™."

Herman Toothrot: "Well, I sailed here with a friend of mine twenty years ago. We hope to discover the Secret of Monkey Island™"

Additionally, this is what Ron Gilbert wrote in the last version of the original Monkey Island game design document: "In a last-ditch effort, the Pirate LeChuck announced he was going to sail to the legendary Monkey Island and return with its secret. The secret was unknown, but legends value it as priceless."

Conclusion:

Whatever the secret is, it is related to the place. It's something that can be discovered going to that island. Also, it can't be related to the events set in motion by LeChuck or by other characters, because the secret of that place was narrated in (presumably old) legends.

When you go to monkey island in the game. Go in the boat and to the top of the island. its shaped like a parrot.i think this is the secret. the secret is about the actual island not the game.