How Bowie Got His Most Unusual Feature

David Bowie may be gone, but that cool gaze will be with us a long time. As any color close-up of him reveals, he had one blue eye and one brown—so how did they get that way? Rumor had it that the pop star was afflicted by a condition called heterochromia, the Telegraph reports. As Quartz explains, heterochromia is rare in people and gives each iris a different color. Yet there's another condition that better suits the legendary singer: Called anisocoria, it makes one pupil larger than the other and mimics the effect of differently colored eyes. Indeed, Bowie had a permanently dilated eye (his left) that prevented it from reacting to changes in light.

That would give it a darker appearance compared to his right iris's natural blue color. Dilated pupils are also more likely to have "red eye," which can add to the different-color effect. But that's all too boring for rock 'n' roll: According to anecdotal history, a 15-year-old Bowie got in a fight with his friend George Underwood over a girl, and Underwood's nail ended up stuck in Bowie's left eye and forever dilated the pupil, the New Yorker reports. It's said they remained friends and Bowie later thanked Underwood for giving him an added "mystique." Get a glimpse of it here in the opening of Bowie's video for "Life on Mars." (More singer stories.)