You can enter the fountain room, and Mordred's laboratory. Take the message from the Maid's room to the second floor of the Mill, where you get the Cosmic Symbols password card. Then you can go under the plaque on the fountain to get the key to the buried door under the hay bales.
(see related question)
Go outside and feed him the robot mouse, and he will follow you into the dungeon. Click the owl and then the fuel rod and he will retrieve it for you.
Follow him out of the lair and feed him the mechanical mouse. Then he will go with you sometimes. To retrieve an object, click Merlin then click on it.
To see the solar system on Astro Knights island, go to the Planetarium. (not part of the game, but an interesting view)
Go on youtube
Get the message and mouse from the Maid's room, and see the King and Queen on the second floor of the castle. (see related question)
You can go to space on Astro Knights
go to the secret door
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
On the Poptropica website, all of the available islands are displayed on the Island Map.
When you feed the robot mouse to Merlin the owl, he follows you. If you click on him, then a location, he will go there. This is useful when the fuel rod is out of your reach in the dungeon.
you run into it and push then there you go