John RitterThe beloved actor played Sam Dorian, JD's father.Elizabeth BanksBanks played Kim Briggs, a urologist who eventually became the mother of JD's son. How did we forget that she was a part of this show?Mandy MooreThe singer played Julie Quinn, who JD dated in season 5.Heather GrahamGraham was the slightly ditzy and spiritual Molly Clock.Tara ReidReid was Danni Sullivan, who has an unhealthy relationship with JD.Michael J. FoxFox used his real-life struggle with Parkinson's disease in his portrayal of Kevin Casey, a doctor with obsessive compulsive disorder.Courteney CoxThe "Friends" alum played Taylor Maddox, a Doctor Who replaces Bob Kelso. Cox works with the janitor to get her fired.Heather LocklearLocklear played Julie Keaten, a pharmaceutical company representative and nemesis to Doctor Cox.Aziz AnsariBefore his days on "Parks and Recreation," Ansari was Big Ed Dhandapani on "Scrubs."Masi OkaOka would go on to land one of the lead roles in the original run of "Heroes." In "Scrubs," he played a laboratory technician named Franklyn.Jason BatemanBateman played a character named Mr. Sutton in "My Big Bird" from season five. JD saves his life, but Sutton doesn't thank him, which leads to another patient's death.