Zach Braff Dr. John "J.D." Dorian Actor Sarah Chalke Dr. Elliott Reid Actor Donald Faison Dr. Chris Turk Actor John C. McGinley Dr. Perry Cox Actor Judy Reyes Nurse Carla Espinosa Actor Ken Jenkins Dr. Bob Kelso Actor Neil Flynn The Janitor Actor Betsy Beutler Katie Guest Star Eliza Coupe Denise Guest Star Aziz Ansari Ed Guest Star Kevin Clash Elmo Guest Voice Eric Jacobson Grover Guest Voice Caroll Spinney Oscar the Grouch Guest Voice Julia Campbell Mrs. Fremont Guest Star David Groyl Mr. Fremont Guest Star Robert Maschio Todd Guest Star Stephanie D'Abruzzo A.M. Muppet (Ex Ray) Guest Voice Lak Rana Another Intern Guest Star Emanuel Gountoumas Little Boy Fremont Guest Star Sokhan Kevin Sar Medical Intern Guest Star Bill Lawrence Executive Producer, Director, Writer