Originally Posted by Shatterhand
About The Monkey Island 2 puzzle...
If you are mentioning the big door in the LeChuck's dungeon... it is a big door with dozens of padlocks, but there's a small door in the big door (Like a "dog's door"). You just have to open that one and ignore all the other doors. Now I remember you had to get a key somewhere in this part of the game, but I don't remember if it was for this door.
The key you're looking for in this part is probably the one behind this door.