Mr. and Mrs. Halford, (the kidney transplant patients) are played by real life husband and wife actors, Scott Rinker and Cathleen Kaelyn. Crew members thought the two were extremely "method actors" until they discovered the two had been married for nearly 20 years.
Carla doesn't appear in this episode.
The episode title, "My Happy Place," is also the name of the theme song of "Corner Gas," a Canadian sitcom that used the same style of cutaway/fantasy scenes as "Scrubs."
When J.D. and Elliot are talking about their relationship and he gives examples on the kind of couple they don't have to be she notices that he watched the Friends marathon. Courtney Cox who starred as Monica in Friends guest starred as Dr. Maddox