Theory that by six or less degrees of separation, every actor is connected to Kevin Bacon, possibly making him the center of the universe. A cult trivia game among movie fans, players choose one actor and create links by naming movies in which they worked with someone, who in turn is related to someone else, and so on, until the final person is directly connected to Kevin Bacon. Created by Craig Fass, Brian Turtle and Mike Ginelli and made famous in 1994 when Jon Stewart invited them to play on his show.
Kevin Costner is one link: Both were in JFK. Julia Louis-Dreyfus of TV's Seinfeld takes all six degrees of Kevin Bacon: She was in Christmas Vacation with Randy Quaid, who was in Major League II with Tom Berenger, who was in Shattered with Greta Scacchi, who was in Presumed Innocent with Harrison Ford, who was in Raiders of the Lost Ark with Karen Allen, who was in Animal House with Kevin Bacon.