The rant referenced in Dr. Cox's rant book is from Season 4 episode 1.
After Elliot states that she has slept at JDs new house every night since he moved, JD states "So we live together." Followed by "I feel like I should've been told." These are the exact lines Michael J Fox's character Michael says in the pilot of Spin City when his girlfriend tells him that she never renewed her lease since she had spent every night at Michael's apartment. Spin City was another creation of Bill Lawrence. Also the main cast of Spin City, minus Connie Britton, often guest starred on Scrubs.