It's never happened...
 

Since the NLDS and ALDS began in 1981, there has never been a year when all four teams in one league were 'post original 16'.

Congrats to the 'new guys':

Houston
Texas
Kansas City
Toronto

And the Cubs win a post season series at Wrigley.

You'd think with all the post-death Mickey Mantle and Ted Williams autographs posted here, that a few people would be interested in modern baseball, but I suppose not.

If it isn't the Yankees, it doesn't exist.