Nature of eyes

No amount of magic, no godly prowess, nothing can ever change the appearance of anyone's eyes. A god or goddess may be able to disguise himself/herself in any form imaginable, but the looks of his/her eyes cannot be changed (see The Colour of Magic). A witch may decide to turn a quadruped animal into a man, or vice versa, but unless the change is permanent, the eyes will look like the eyes of the original species (see Witches Abroad).