Greene says to Carter "You set the tone". This was what was said to Greene by Dr. Morgenstern in the pilot episode.
Stan Sidel (Ken Lerner) was also in series 1 episode 4, when his cell phone kept setting off electronic devices in the ER. In both episodes he is treated by Dr Greene.
The patient with a painful hangnail in the bed next to homeless Al, is also in the pilot episode (1:1) as hypochondriac patient Mrs Raskin (Julianna McCarthy) who it is implied, comes to the ER often for hangnails or minor ailments as she is elderly and likes the company.
The character Stan Sidel is based on real-life Hollywood writer Stan Siedel, who died 2 years before this episode was released. He is credited as a writer on this episode.