The Supply Room door has a key, which you receive when you get the museum job.
The underground entrance is locked with the Dragon Face lock.
The house in the Countryside is only unlocked later in the game when you receive the key.
It is for to unlock the door when you go under ground for this undrer ground tunel tour the door with the dragon face leads to the supply room in the Museum.
First go to skullduggery island,take your ship to a island called Keys World island and you will find the key of the chest on counterfeit island!;)
If you are referring to the keycard in Poptropica Counterfeit Island, you use it to unlock a door in the secret lair, which can be found in the countryside. It is locked so you have to find a key.
you go out the door!
go in thru the back door
you have to go to counterfeit island
Since you couldn't find a key to unlock the cottage in the Country Side, this is probably it.
go to the guy near the door. talk to him.
In the Clown Shop.
You do not have to find the key. It is given to you later in the game.
You use the key from the Curator to unlock the Inspector's house in the CountrySide.
First, you have to find all the pieces of paper around counterfeit island. When the pictures are assembled together, it will show a picture of a dragon. Make sure the dragon on the door is the same as the dragon in the picture.