After the dart players in the bar hit the balloon, talk to them again and tell them to hit the post on the right hand side of the screen. Talk to them again and tell them to hit "That guy over there". They will throw the dart at the screen and it cracks.
Frankenstein
Talk to Deadeye Dave about free prosthetic parts until you get a butt, head, liver, foot, stomach, guts, heart, and skin. Combine everything but the skin to make Frankenstein.
Hidden items
While at the school, ring the fire alarm. Mrs. Rivers will run out. Quickly run inside. Look at the treasure chest where you find the whistle. There will be more items inside. Grab one. Mrs. Rivers will catch you and throw you out. Repeat this to get eventually get everything but the wad of tobacco.
Hidden sequence
Successfully complete the game and wait until all the credits complete to see an epilogue sequence.
Kill Guybrush
In the Swamp in Lucre Island, when the other Guybrush gives you the gun, you can shoot him with it. The gun must be one of the first three things he gives you.
Murray Bites
Change in the tent at the diving contest about 12 to 13 times in a row.
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Murray's head
Type skull during game play and Murray's head will appear with his laughter. Press U to remove the head.
Play Pong with Murray
Keep spinning the stool he is on -- to do that try picking him up. When he starts repeating the same warnings to you, face Guybrush the other way and type murryball.
Run easily
To make Guybrush run without having to hold [Shift], press [Up] + [Forward] twice and hold it.
Crack the screen in Scumm bar...