Welcome to Gaia! ::

Jill Tracy [Nicole Sullivan]-flighty and nervous recurring patient,known to suffer from depression and relationship problems, which became more extreme up until the day she died (( of rabies )).
Alex Hanson [Elizabeth Bogush]- a social worker at the hospital and who dated J.D. during the first season. She was revealed to be a drug addict.
Sam Dorian [John Ritter]- J.D's Father. ((Died of a Heart Attack))
Kristen Murphy [Kelli Williams]-Turk's medical student and Dr. Cox's love interest.
Sean Kelly [Scott Foley]-Elliot's two-time ex-boyfriend
Ben Sullivan [Brendan Fraser]- Jordan's brother and Dr. Cox's best friend ((Died of a heart attack, but had leukemia))
Dan Dorian [Tom Cavanagh]- J.D.'s sneaky older brother
Julie [Heather Locklear]-a representative of a pharmaceutical company,Had a relationship with Dr. Cox which lasted less than a full episode.
Kevin Turk [D.L. Hughley]- Turk's rambunctious brother
Marco Espinosa [Freddy Rodriguez]- Carla's brother and Turk's nemesis
Paul Flowers [Rick Schroder]- slightly controlling murse whom Elliot dated
Jamie Moyer [Jamie Smart]- J.D.'s drama-creating one-time love interest T.C.W
Spence [Ryan Reynolds]- J.D. and Turk's deadpan college buddy
Danni Sullivan [Tara Ried]- Jordan's sister and J.D.'s two-time ex-girlfriend
Dr. Molly Clock [Heather Graham]-attending psychiatrist,J.D. had a crush on and was Elliot's friend and mentor
Neena Broderick [Julianna Margulies]- as cold-hearted malpractice attorney
Murry Marks [Matthew Perry]- the son of a patient who needed a transplant from his son
Jake [Josh Randall]- Elliot's 'now' ex-boyfriend
Paige (Cox) [Cheryl Hines]- Dr. Cox's born-again Christian sister who reminds him of their troubled childhood and abusive father.
Mrs. Wilks [Michael Learned]- kind and genial patient whose lengthy stay at the hospital and apparent recovery ((were ultimately for naught when she succumbed to an unexpected infection.[))
And Many More....