When Dr. Cox is discussing how to treat Mr. Barnes with Elliot and J.D., Elliot is holding a patient's chart with the name 'Al Czervik' on it. That is the name of the character played by Rodney Dangerfield in Caddyshack (1980).
Doctor Cox mentions Will and Grace in this episode. Sean Hayes, who previously starred as Dr Murdoch in S1e7, is a main character on Will and Grace.