Responding to Kimmel's claim that, were he to become president, the first thing he'd do is find out whether Area 51 actually holds proof of intelligent extraterrestrial life, Clinton said that he once instructed some aides of his to do exactly that. They didn't find much, but Clinton told Kimmel that, if they had, he would've been sure to tell the American people.
Clinton then transitioned into an explanation for why he considers it a real possibility that, one day, Earth will be visited by intelligent life from another world. He cited the enormous size and rate of expansion of the universe to bolster his argument.
After stressing that his ultimate answer to the question of alien life is "I don't know," Clinton said, "If we were visited someday, I wouldn’t be surprised."
"I just hope that it's not like 'Independence Day,'" he joked.
You can watch a clip of the interview below, via Jimmy Kimmel Live: