When Barney enters the courthouse, three of Opie's checker pieces move two spaces over to new positions on the checkerboard (an impossible move in Checkers) and a new Opie checker enters the game, alongside Andy's desk, in place of an Andy checker that has slid two spaces towards Andy (an impossible move in checkers as it, at the very least, isn't kinged).
At the checkerboard, Andy leans his left elbow on his desk. In the two-shots, his left forearm is raised as if leaning his head against his hand, but in straight-on one-shots his left forearm crosses down before his navel.
Near the end as Barney and Thelma Lou are talking in front of the doors of the courthouse, the shadow of the boom mike pops in to the right of Thelma Lou on the door as they're talking.