You can re-enter the dungeon through a tunnel from Mordred's underground laboratory (under the hay bales on the farm). Feed the mouse ot the robot owl, then push through the mud wall, go down the tunnel, and enter the cell. When the robot self-destructs, click the owl then the rod and Merlin will get it for you.
(see related question)
There is no jail on Astro Knights Island. There is a castle dungeon, where an attacking alien robot is being held after his capture. (see the related question)
Throw the switch when you get the cheese. You can enter the dungeon from Mordred's underground laboratory once you have the robot owl. (see the related question)
Feed the robot mouse to the owl, and then he will follow you. In the dungeon cell, click the owl, then the fuel rod, and he will retrieve it for you. (see related question)
Go to Mordred's tunnel and you'll see the robot. Get the fuel rod and then go to the ship. From then on, you'll be in SPACE!
To see the solar system on Astro Knights island, go to the Planetarium. (not part of the game, but an interesting view)
Since you can play the planets in any order, the third robot could be any of the "boss" creatures on the planets. (see the related questions)
For hints only, see the Poptropica blog (related link). To see all questions about Astro Knights Island, type Astro Knights in the ask bar above. For a complete solution, see the related question.
The phoenix eggs on astro knights island are in space.It is in jungle planet.To go in space you have to crash the small ship and build your own ship.Go to jungle planet and jump on the things swinging until you land on a robot platform kind of thing.(Watch the robot worms) Go right and you should see the phoenix eggs.
Solve the door puzzle (he's Mordred) and battle his robot warrior suit. (see related questions)
You get the replacement green FUEL ROD for the SAUCER Excalibur from the robot invader in the dungeon. (see related question)
The object of Astro Knights is to get into space using the crashed saucer Excalibur. Once there, you travel to three planets inhabited by robot creatures and defeat them. Then you can travel to the lair of the villain to rescue the Princess. (for a complete solution, see the related question)
Poptropica. (see related link)