Arthur was a short, blind boy who had to constantly be turned toward the direction of what he was supposed to be looking at or who he was talking to or listening to. He asked his uncle Merlin to create some sort of glass object to improve his vision, but Merlin said such things would be considered witchcraft.
As a normal kid, Arthur has light red hair in a bowl cut, and wears a green tunic. When he puts on Mr. Turner's glasses, his muscles suddenly rip through his shirt and he is in black pants, his hair also becomes long and flowing and he wields the sword in the stone that Timmy actually pulled out, but later gave to him.
When Timmy Turner shows up in his time period and gives him a pair of his Dad's reading glasses, Arthur puts them on and it is immediately transformed into muscly superhero with long flowing hair. Timmy then hands him the sword that he was using to fight the dragon He attacks the dragon that was terrorizing his people, and is burnt into a skeleton, but Cosmo and Wanda manage to bring him back to life and he manages to easily kill the dragon the second time around. As a result he becomes the new king and decides to create the Knights of the Round Table. His uncle then wanted to be with him since he'll be rich. After looking at Timmy, Arthur then knocks Merlin off the mountain and right where the starving villagers are.