J.D. is also engaged in a constant battle with the Janitor (Neil Flynn) from the very first episode. The Janitor is trying to open a jammed door when J.D. suggests there may be a penny stuck in it. When it turns out that there is a penny stuck in the door, the Janitor vows revenge. Throughout the series, the Janitor frequently plays tricks and pranks on J.D. In the eighth-season finale, it is revealed that J.D. "did" accidentally put the penny in the door. The Janitor saw him drop the penny, but because he never admitted it, decided that J.D. had failed a "test of character," thus igniting their feud.