The Mad Scientist, also known as the Strange Man, the Persian Scientist or simply the Scientist, was a human being.
This strange man with an eerie glare lived in a creepy house not far from Donald Duck's by the late 1940's, when he finally completed his investigation into the secrets of the Driers of Itsa Faka. Having discovered how to revive long-dried Itsa Fakans, he flew his concealed plane to a desert in Iran and had Donald Duck and Huey, Dewey and Louie Duck (whom he had abducted to use as a workforce after the kids peeked a little too closely into his experiments) dig up the ruins of Itsa Faka.
After he revived King Nevvawaza and his retinue, the Scientist obsessively pestered the ancient Persians with one question: how were they dried in the first place? What was the process? The murderous madman soon found the Radium Vapor himself and revealed the full extent of his plan: he intended to wipe out all organic life on Earth using the Vapor, to remain as the sole proprietor of the entire world. His dreams of conquest were cut short when the seal on the Dust Bowl containing the Vapor was broken, turning the Persians back into dust and the Scientist with them (while Donald escaped by hiding in a tub of Solution).
Behind the scenes
The Mad Scientist is the main antagonist of the 1950 Carl Barks story In Ancient Persia. His physical design appears to have been inspired by the Mad Doctor, though they are understood to be different characters in-universe.