Trivia & Secrets
There is a useless option on the menu similar to the 3D acceleration joke from The Curse of Monkey Island. In the menu go to "Options", then "Alter Gee Whiz Factor..." and finally "Multiplayer Options...". Every time you try to change it you will get a funny message.
The duck goes moo
If you use the canard several times he will eventually do a moo instead of a quack. Guybrush will also comment how weird that is.
Abomination of Nature
When you go to the prosthetics shop you can ask Deadeye Dave for free prosthetics. While he is telling a story you can provide different names and you will get different parts. If you get a heart, liver, stomach, butt, head, feet and intestines and then combine them together you will end up with an abomination of nature which you can even use.
Guybrush needs to resurface after 10 minutes
If you leave Guybrush underwater for more than 10 minutes, near Ozzie's secret hideout on Lucre Island, he will go back to the surface as he can't hold his breath any longer.
Guybrush kills himself
When Guybrush meets future Guybrush in the Mists of Time he gets several items from him. One is a gun which you can use to kill him. When you try to leave Guybrush will be warped back into the beginning.
Barrel of Coupons
After you get the Planet Threepwood free coupons from Stan and also from the Micro-Groggery, a barrel of coupons will mysteriously appear outside the Micro-Groggery. This will allow you to avoid repeating the Stan's pitch puzzle in case you need another coupon.
Play pong with Murray
To play the mini-game you have to spin Murray several times on the stool until he starts repeating himself. You can do this by picking him up. Once he repeats himself turn Guybrush around until there is no option on the bottom of the screen and type "murrayball".
Certificate of Transmogrification
If you get correctly all answers to Ozzie Mandrill's Pirate Transmogrification Academy final exam ie. replying with the nicest answer, Guybrush gets a "Certificate of Transmogrification" which he is not proud of.
Murray kicks Guybrush out of a tent
If you enter 13 times in a row inside Marco Pollo's tent in Jambalay Island Guybrush will get kicked out by Murray. Guybrush will then kick Murray and get back in the tent.
Type skull and Murray will appear
This only seems to work while Guybrush is on Monkey Island. If you type "skull" a laughing Murray will appear on the screen.
Three-headed monkey in Monkey town
If you wait a long time (from 15 to 30 minutes) in Monkey town, a three-headed monkey will appear inside the first hut on the right.
Escape key during final battle
If you press the "Esc" key while you are fighting LeChuck during the final battle, Guybrush will comment "I don't think it's that easy" as the key can usually be used to skip cutscenes.