Bring up aliens and a lot of people will scoff. But not everyone is laughing. Around the turn of the century, 3.8 million people banded together in a real-time search for aliens — with screensavers.

This November, the Predator returns to the big-screen in Dan Trachtenberg’s Predator: Badlands. Since the release of the original film back in 1987, the alien trophy hunter has become a pop culture ...