First time the three main characters (Jake, Charlie and Alan) sing into one microphone during the opening credits.
Episode title spoken by Alan, to Charlie.
When talking about Jake, Alan says "He's never been spanked, he's never even been yelled at." This explains why Jake is such an obnoxious spoiled brat throughout the entire series.
The shrink to whom they bring Jake is a child shrink, her office is set up for children. Later in the series, when Alan and Charlie and Walden go to her for help, her office is set up more for adults.