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.
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.
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)
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.
you fight the robot on jungle planet
One of the robot attackers was captured and put in the castle dungeon.
Things that Zap you on Poptropica : Lasers (Spy Island) Electrified Windows (Spy Island) Mini-Bots (Spy Island) Electric Fence (Diamond Mine, Nabooti Island) Electric Caterpillars (Jungle Planet, Astro Knights Island) Mordred's Robot (Astro Knights Island)
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)
When you awaken the robot owl Merlin, he flies out of Mordred's lab. In order to get him back, you have to feed him the robot mouse. (chomp)
In the final battle in the hidden galaxy, Mordred's robot warrior suit fires short bursts of red lasers to "zap" you. You can tell when it is about to fire by the glowing red spot on the robot's chest. You can dodge them if you move just as they fire.
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)
One of the robot attackers is in the castle dungeon. The alien ships attack you in outer space when you are near the Fire Planet and the Jungle Planet. Dodge their shots and shoot back, and land as soon as you can.
In the Maid's room (castle first floor left), feed the cheese to the robot mouse.