The telephone number of W.B. Jones Heating and Air, one of the "Five Families" mentioned by Kevin, is (800) 984-3672. If you had called the number you would get a prerecorded message encouraging you to keep your thermostat set at 67 degrees in the wintertime and 76 degrees in the summer to stay comfortable and decrease your carbon footprint. The message concluded with an invitation to wait for the next available customer service representative, but disconnected after about 30 seconds of elevator music. The number no longer works.
In the scene with the "Five Families", one of the actors, Paul Faust was the only first-time actor. Faust is the cousin of writer Paul Lieberstein, and had been on a tour of the set and talked to many of the writers. He made a good impression and so the character of "Cool Guy Paul" was based on him. The day before they were scheduled to shoot, the show still had not cast anyone for the role, so they called Paul in New York City and had him read the lines into a camera and e-mail to them. In less than an hour, Faust had landed the part and was flown out to Los Angeles.
Originally, Novak wrote for Jim to put Dwight through a "phony management training," but NBC pointed out that it felt like the writers had done it before even though they had not. As a group, the writers tried to think of a new idea for the plot; they considered having Pam move in with Jim, but they thought that first the two should be engaged.
The trivia item below may give away important plot points.
When Michael asks the office to set him up with one of their friends, Jim jokingly tells Pam that he is going to set up Michael with Pam's mom. Later in the series, Michael does start dating Pam's mom.