The Jetsons - Season 2 Episode 12 -

Two scientists remove a block of ice holding an alien creature from a frozen planet. Upon returning to Earth, it slips from their grasp and thaws out on the Jetsons' barbecue. They believe him to be their alien cousin who's arriving for a visit. The scientists then realize they have to return the alien to his homeworld before his people realize he's missing and a resulting war will break out.