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)
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)
One of the robot attackers was captured and put in the castle dungeon.
Actually, Merlin has little to do on Astro Knights Island. He recovers the fuel rod from the dungeon when the robot self-destructs. And he battles Mordred at the very end of the island.
Still in the dungeon. Either the hole is too small, or he doesn't like dirt caves.
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 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.
There are no cubes on Astro Knights island. There are ice floes on the Ice Planet, that you jump across to avoid the robot fish.
You get the replacement green FUEL ROD for the SAUCER Excalibur from the robot invader in the dungeon. (see related question)
Merlin the robot owl will follow you in the underground lab once you feed him the robot mouse (ouch). He can retrieve the fuel rod from the dungeon after the robot explodes. Just click on Merlin and then the fuel rod.
The robot in the dungeon never does anything but blow itself up. The robot warrior suit worn by Mordred attacks continuously. If it stops, you need to reboot and play the castle battle again from the start.
The green fuel rod on the Excalibur is broken and needs replacing. There is a rod inside the robot invader in the dungeon. (see related question)
you fight the robot on jungle planet