Over the course of several shows ,Bob's office number keeps changing. In some shows it's 715 and others it's 751. In a season 2 show ,the door reads 715 and then we go into his office. Later ,when he and a patient leave ,it's back to 751 again.
Shortly after Howard, Jerry, and Carroll arrive at the Hartley's apartment . . . with none of the characters in the area . . . the shadows of crew people can be seen moving across the back cushions of the couch.