As you know, this character from For the Frog the Bell Tolls has been a recurring face throughout the Wario Land series, both in the form of an enemy (Mad Scienstein in Wario Land 3 and Dr Mario 64) and a sorta ally (his scientist persona in Wario Land 4).
I really like his role in Wario Land 4 as another explorer of the Golden Pyramid, oblivious to most of what Wario is encountering and just there to research before abandoning ship once the pyramid starts to collapse. That mini-interview he had on the Japanese WL4 website... sure is something, as well!
Definitely 4. It was so much fun to abuse the hell outta that guy. Also the reason his head looks different in 4, was because he had a light surgically transplanted in there.
