In the undergroud part of the libary
To obtain the moldy cheese in Astro-Knights on Poptropica, you need to first find the rats in the secret dungeon. They will steal the moldy cheese from you, which you can then retrieve by using the Rat Trap item in your inventory.
you put it in the room with the mouse in the astro knights castle and the mouse will eat it
If you mean Poptropica, you can get the rat when you go to the castle and go to the left door, give the Moldy Cheeseto the rat, and he will come to you.
Just beat Mordred and she'll be free
get the moldy cheese from the basement of the castle and lay it out in the bed room
Go to the Library. Go to the M section. There is a brick that you can press.there reveals a dungon. IGNORE THE ALEIN!!! You will pick up some moldy cheese. Go where the mouse is. Put the moldy cheese down. The mouse will eat it. And THEN capture it.
In the Maid's room (castle first floor left), feed the cheese to the robot mouse.
There is no fish. You have to get the mouse from the madian's room and feed it to Merlin. You lure the mouse with the moldy cheese you get from the dungon.
you go inside, get the moldy cheese and pull the lever down.
In the Maid's room (castle first floor left) you will find a mechanical mouse.
you need the hovercraft,mouse,moldy cheese, owl,green glowy thing,coordinates, and find the broken paceship.
The only place is in the castle dungeon, below the library. (see related question)