Charlie mentions to Alan that, had he known their mother would have sex in his car, he would have ordered the vinyl seats. Modern Mercedes-Benz cars do not have vinyl seats, only leather or cloth.
During season 2, Jake, Alan and Charlie refer to Judith's new boyfriend, Dr. Melnick (Ryan Stiles), as "Greg". Halfway through this episode, it is revealed that Judith and "Greg" have broken up. In future seasons, Judith again dates (and marries) Dr. Melnick, but his first name has changed to "Herb".