It was a skit that was done for Comic-Con in 2009, for the panel about the show Lost. All copies of the video I could find online were bad, this was the best I could find. I’m not sure there’s an “official” video available anywhere (if so I failed in finding it).
But yeah, he’s another example of another man with naturally dark eyelashes.
My WAG is that the practice of wearing eyeliner comes from a history of people trying to imitate that natural feature some people possess. We are so familiar with the practice of wearing eyeliner that when we see someone who has it as a natural feature, it’s assumed that eyeliner was involved.