Kiss of the Spider Monkey is the second to last chapter of The Curse of Monkey Island.
It follows Part IV: The Bartender, The Thieves, His Aunt, and Her Lover and precedes Part VI: Guybrush Kicks Butt Once Again.
--Monkey Island - Carnival of the Damned-- You start out in a locked compartment of one of LeChuck's Dynamonkeletric rides. LeChuck is to your right and he's holding Elaine captive behind him. Guybrush can talk all he wants about the amusement park here at Big Whoop and other things that are coming up like the demise of all of the governor Marley's crew members. When you are done talking select the "I've heard quite enough of your horrible stories" option and Guybrush will childishly hold his hands over his ears and doesn't listen to LeChuck anymore. The zombie pirate will then put a curse on you and leaves the scene with Elaine. Open the door of the ride and you'll find out that it isn't locked at all. Once Guybrush walks out the door you are about to find out what kind of curse he received from LeChuck. After a few moments you find out that he has been turned into a child himself!
--Carnival of the Damned--
Guybrush will tell you that he needs to get on the Rollercoaster of Death, because that is where Elaine is. He also tells you that he feels like he is having a severe headache which causes a brain freeze. These are similar symptoms of a person who feels drunk. Remembering the recipe for hangover remedy we need to find some Egg, Dog Hair and Pepper (or surrogate / substitutes).
-Pepper- The easiest ingredient to obtain is Pepper in the shape of a Pepper Mill and can be found near the Ice Cone guy on his booth.
-Hair of the dog that bit you- There is only one dog around and that is the goofy dog actor called Dinghy Dog. Push him 3x (or 6x in MM) and he bites you, because he will get annoyed of all that pushing. Guybrush will automatically collect some hair from his dog suit costume.
-Egg- If you look around there doesn't seem to be anything related to an egg, but there is actually one thing that is made from egg: Meringue. Look at the staple of pies near Wharf Rat and talk to him to find out that the pies are made of is concoction with eggs in it. The question remaining is how to obtain it from him. You can't just steal a pie from him, so we need to do something differently. As you may have noticed Wharf Rat get annoyed very easily so if Guybrush would stick his head through the spot where Monty Meringue the Mime is he can surely get a pie in his face so to obtain the egg surrogate.
Hence we must get rid of Monty Meringue first and this can be done by creating a heavy pie. Go to Dinghy Dog and ask him to guess your age. With your childish look Dinghy dog guesses that you are just about 7 years old. Then Guybrush shows him his SCUMM Actor's Guild Membership Card and proves to him that he is 20 years old (I never knew he had a card like that). Guybrush is then allowed to pick an item from the booth. There are many prizes and personally I would have picked Murray, but if you do so Guybrush will automatically reconsider for the Anchor. So no matter which prize you choose you will always end up with the little Anchor. Of course Murray will be upset about this, but there is nothing to be done about it.
In a regular game you can just sneak the Anchor in the Pie Stack. In Mega- Monkey you can't do this however! Instead, look in your inventory, pick the Pie Pan, use Captain Nick's Shaving Soap on it to create a fake pie and increase its weight by putting the Anchor in it. Select this Heavy Fake Pie and put it on the stack of regular pies. Guybrush will then automatically ask Wharf Rat to shoot the cannon and once he obliges the shot will take out Monty Meringue in the process. You can walk through the back gate from this moment on, since the Mime player is gone and look through the gaping hole. This will upset Wharf Rat and he shoots a Meringue Pie at you. As Guybrush wipes his face clean he will put the Egg surrogate in the inventory.
-Mixing it all together- The last step is to go to the Cone Guy again and have Guybrush ask for the plain cone (A Merry, ho ho ho, Christmas Cone would have been nice too). Don't walk around with the cone or it will melt down very quickly. Open the inventory and use the Pepper Mill, Meringue and Dinghy Dog's Hair on the Cone and you will end up with a Disgusting Cone. Eat it and Guybrush returns to his normal self once again.
Walkthrough by Iron Knuckle