On September 29, 2012 playing in Busch Stadium against the St. Louis Cardinals with the bases loaded, Morse hit a line drive to right field that bounced off the top of the fence. The ball was initially called in-play and Morse was tagged out trying to take second base. The play was eventually reviewed by the umpires, who ultimately overturned the call and pronounced Morse's line drive a grand slam home run. To ensure that none of the runners passed each other on the basepath, Morse was instructed to round the bases clockwise back toward the batter's box at home plate, take a mock swing at a nonexistent pitch, and then run counter-clockwise around the bases, like a usual home run. After the season, he was awarded with the GIBBY Award for Oddity of the Year.