Okay here's the plot moreover.
The game opens with Elaine at the end of Monkey Island 2, standing on top of the remains of the "X marks the spot". She says her line from the last game, and it cuts to little Guybrush and
"Chuckie" walking out of the tunnels and into the Big Whoop Amusement Park. the rest of MI2's ending plays out and then on the next screen Guybrush's parents turn back into skeletons and fall to pieces on the ground right next to the Madly Rotating Buccaneer (yes, I want to finally make a visual representation of that thing), while Lechuck turns into his true form which I'll have to think of later. Lechuck beats Guybrush with a porcelain vase and knocks him out. He awakes in a room of right now no description, let's say it's Stan's coffin for now, and we are faced with a Phatt Island jail stype scenario.
That's all I have so far, and I know it's a bit rough, but with your help and some fine-tuning I'm sure I can make it a bit better.
"There was an old farmer who lived on a rock,
he sat in the meadow just shaking his..."-The assumption song. A random youtube search can bring on a big laugh.