The house in which JD's flashback is set (with his dad played by John Ritter) is also the house used in Ritter's comedy 8 Simple Rules (2002).
This is the first episode in which the Janitor does not make an appearance.
The premise of this episode for JD is that he makes a rare diagnosis of necrotizing fasciitis, but just a couple episodes previously, Eliot was upset over a patient with that same diagnosis who died after she elected for surgery.
In this episode there is a flashback of JD and his dad where he gives JD a bicycle bell and then says he will give him different parts each year. The background set of this flashback is the 8 Simple Rules living room, which he was starring in at the time.