Nope, no jokes on my part. Instead, just a link to my favorite prank of all-time, George Plimpton's Sidd Finch story.
A second flap down by the pitcher's end was drawn open, and a tall, gawky player walked in and stepped up onto the pitcher's mound. He was wearing a small, black fielder's glove on his left hand and was holding a baseball in his right. Christensen had never seen him before. He had blue eyes, Christensen remembers, and a pale, youthful face, with facial muscles that were motionless, like a mask. "You notice it," Christensen explained later, "when a pitcher's jaw isn't working on a chaw or a piece of gum." Then to Christensen's astonishment he saw that the pitcher, pawing at the dirt of the mound to get it smoothed out properly and to his liking, was wearing a heavy hiking boot on his right foot.