User blog comment:Aithusa07/List of Plotholes from Merlin/@comment-10341849-20130718115816/@comment-5102537-20130719141216

Edrea wrote: "About Mordred, I think it is reasonable if Arthur forget him. With so many villains and enemies, Arthur might not remember him at all. After all, at that time, Mordred was not the enemy, he only considered enemy because he was a druid."

One would think that such an act - freeing a druid boy and resucing him from death, plus betraying his father's trust, law and direct orders, which was extremely risky - would be something to be remembered. Arthur also asked Mordred what his name was when they parted in the woods. It's highly unlikely that Arthur forgot.

As for Aithusa, I think they messed up the entire story. Shame, Aithusa would have had so much to contribute, yet they chose to use him or her as some sort of a side-effect and tool for being responsible for wounding Arthur beyond recovery or healing magic. Season four and Aithusa's first description was being changed for plot convenience in season five.