You can't "costumize" (copy) Mordred in the game, but you can find users in the multi-player room that have his "cyborg" face, and copy those.
Since Mordred / Binary Bard only appears in the pre-recorded scenes of Astro Knights Island, you can't use the Costumizer. You may locate someone on the islands who copied the Bard when he was promoting the island in May 2009.
The Binary Bard is revealed as "King Mordred, Master of the Universe". (see related question)
The costumizer does not work on the scene sequences, only on the interactive characters. If you want to look like Binary Bard or Mordred, you will need to locate an identical individual (or figure out the code for the randomizer).
Mordred was a scientific genius, inventor, and former ruler of the Kingdom of Arturus. His experiments with cyborg organisms was decried by the populace and he was deposed. Years later, the solar system is raided by the robot forces of the Binary Bard, who has built creatures much like Mordred's designs. When the Princess is kidnapped from Arturus, space knights are sent out to rescue her.
You can't costumize him in Astro Knights Island or Super Villain Island but you might search the common rooms for someone with his face.
On Astro Knights Island in Poptropica, pretty much like classic knights (armor, cloaks, swords).
You put the green thing that looks like a glow-stick in the slot in the UFO, then you find the coordinates for Mordred, I can't remember where to find them, then you enter Mordred's coordinates and off you go!
She isn't on a planet.she is on a asteroid (if you are talking about astro-knights island)
There is an image at the related link. (see the related question)
kings island is coming out on poptropica after reality tv like astro - knights came out aftr big nate
Because on Poptropica it showed it as a another different planet on Poptropica like astro-knights island. (not exactly)
The dragon is mechanical, like all of Binary Bard's creations. (see the related image link below)