Dr. Weil, like many characters, underwent several different designs in the conceptual stages. His designs were based on three different ages: young, middle-aged, and old. Ultimately a variation of the old design was chosen, but there are notes of interest about his other designs as well. The young design was meant to pilot a giant exoskeleton, and before being revealed as a young man his silhouette was meant to be seen with glowing eyes that made him appear more monstrous. The middle-aged design bears some mild similarities to Doctor Wily, though Inafune has firmly denied Weil and Wily were directly connected in any way. This design was later used for a minor character in Mega Man ZX Advent.