I had never heard this story, but it sounds like something straight out of Bull Durham:
On Aug. 31, 1987, Dave Bresnahan was the Michelangelo of potato sculpting. He sacrificed five fine tubers to the spud gods – death via peel – before settling on the correct shape. He drew red lines on the winner to simulate seams, only to see them erased by the potato's weeping. He wielded that peeler like a true artiste.
Because in order to pull off the greatest prank in baseball history, Bresnahan needed to shape a potato like a baseball.
Now if only someone would try the gag out on a major league stage...