get the moldy cheese from the basement of the castle and lay it out in the bed room
the mouse is in the princesses room in the hole in her wall but you have to get the cheese to get him/her.
release it to the owl. then the owl will follow you
give him the robot mouse from the cell
The mouse will get surprised, run around, then run back to you.
You scare the owl outside. follow it and release the mouse. it will know follow you
you put it in the room with the mouse in the astro knights castle and the mouse will eat it
It is a mechanical mouse. (see related question)
Click on his card in your items bag.
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.
go inside the place where the king and queen lives at the corner on the right
go to the princesses maid's room and use it you will get the robot mouse
Find the old cheese. . Give the cheese to the mouse and give the mouse to the owl.