I may have posted this somewhere on this forum in the past, but there's a really weird coincidence involving the Trek episode "Metamorphosis". There's a scene where the character Zefram Cochrane (played by guest star Glenn Corbett) has been reluctantly convinced to lure the companion into the trap the Enterprise men have set. Before he goes out to summon the entity, he delivers the line "What was it they used to call it? A Judas goat?"
A year later, on Irwin Allen's Land of the Giants, virtually an identical line was spoken by that series' star Kurt Kasznar in the episode "Weird World". What makes this coincidence even more remarkable is that Corbett just happened to be that week's LOTG guest star.
But wait, it gets even stranger. Several years earlier, on a 1963 episode of Route 66 entitled "Somehow it Gets to Be Tomorrow", Martin Milner also said nearly the exact same line (albeit Milner used the term 'sheep' instead of 'goat'.) A few episodes later, guess what actor joined that series as Milner's new co-star?