How do you get the key in poptropica vampires curse island?

There are keys on several islands on Poptropica :

• Shark Tooth Island : the "translation key" is a page from Professor Hammerhead's Journal. The "key ingredient" is for the shark potion.
• Big Nate Island : if you recover his lost lobster trap, Cap'n Salty will give you the key to his jet ski.
• Astro Knights Island : the small key opens Mordred's underground lab. The Golden Key opens the path to Mordred's hideout with the portal on the crystal asteroid.
• Counterfeit island : the key opens the Inspector's house in the Country Side. You cannot find it, but it will be given to you during the game. Another key fits the door to the supply room, and you get it when you pass Forgery Training.