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.
Nothing. When you defeat the giant robot, you take the Orb back to Arturus and Mordred is left behind in his castle. You receive the island medallion.
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)
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)
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!
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)
First, you jump, because Mordred is taking a potshot at you, too! You go back to playing your own character. Duck down and wait for the robot to come right over you. Jump up and climb on the robot to get to the princess. Then you jump to one of the chandeliers. The robot tries to zap you but it hits the chandalier instead. It falls on the robot. You do the same to the other chandelier. When Mordred tries to take the orb the princess stops him. And you have finished Astro Knights!
Solve the door puzzle (he's Mordred) and battle his robot warrior suit. (see related questions)
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.
Solve the puzzle door and enter to fight Mordred's robot suit, first as Merlin then as your character. (see related question)
There is nothing you can do about the robot invader. Collect the sheese and pull the switch that opens the rear hatch in the cell. When you follow the tunnel from Mordred's laboratory, you enter the back of the cell, and you will need the owl to recover what is left of the robot.
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.