For years, it seemed like nothing could kill ER.

Not falling ratings. Not massive cast turnovers. Not Kellie Martin as a straight-laced medical student.

It’s no secret that the aging medical drama has been on life support the last few seasons. If ER were a dying patient, the plug would’ve been pulled a long time ago.

More early cast members: Kellie Martin, Gloria Reuben, Julianna Margulies, Laura Innes, (back, l-r) Anthony Edwards, Eriq La Salle, George Clooney, Alex Kingston, Noah Wyle.

But good TV shows never truly die. They just glide to that wonderfully lucrative afterlife called syndication.

TOP 5 ‘ER’ MOMENTS

1. Woman dies giving birth: Dr. Greene (Anthony Edwards) feels responsible when a pregnant woman whose life he attempted to save meets a tragic end. The sight of Greene breaking the news to her grief-stricken husband (Bradley Whitford) and of Greene silently crying on the El train ride home still puts a lump in my throat.

2. Doug and Carol reunite: Nine years ago George Clooney filmed a secret, two-minute cameo in Seattle in which the hunky doc reunited with the love of his life (Julianna Margulies). Word is a record number of Kleenex tissues were used that night.

3. Dr. Greene checks out: OK, so it felt like Greene’s death by brain tumor took, like, three seasons. But the bespectacled chief resident was the heart and soul of ER for so long, we quickly forgave him for taking forever to die.

4. Dr. Robert Romano is killed in a freakish helicopter accident: If you remember Romano (Paul Crane), he was loud, obnoxious and crass. Having a helicopter fall on him was the perfect way for him to go.

5. Jeanie Boulet living with HIV: For years, the soft-spoken physician’s assistant (Gloria Reuben) became the public face for the dreaded virus. No other prime-time network series had ever featured an HIV patient determined to continue with her life and career. But I still haven’t forgiven the writers for how they let Jeanie sheepishly slink away during Carol’s baby shower. Nixon got a better dismissal.

THE EARLY CAST: (From left) George Clooney; Eriq La Salle; Sherry Stringfield; Anthony Edwards; Gloria Reuben; Noah Wyle; and Julianna Margulies.

THE ORIGINAL CAST: Where are they now?

ANTHONY EDWARDS

(Dr. Mark Greene)

Years in the ER: Eight

Why we loved him: Because if you were dying and hooked up to a bunch of IVs, Dr. Greene was the kind of caring doctor you wanted holding your hand.

Life after the show: Played a cop in the movie Zodiac and Julianne Moore’s husband in The Forgotten. Returned to ER last November in a flashback scene with that cold fish otherwise known as Dr. Cate Banfield (Angela Bassett). Possibly still counting all the dough he made off the hit medical drama.

ERIQ LA SALLE

(Dr. Peter Benton)

Years in the ER: Eight

Why we loved him: No one played gruff and obnoxious better. Was also one of the few strong black male characters on TV.

Life after the show: Spent more time behind the camera than in front of it as a director (Law & Order: SVU, Without A Trace) and a producer.

NOAH WYLE

(Dr. John Carter)

Years in the ER: 12

Why we loved him: The baby face. The dimples. The doe-eyed expressions. Should I go on?

Life after ‘ER’: Did his Indiana Jones thing in three Librarian TV movies; played George W. Bush’s secretary of commerce in W., returned to ER for several guest stints.

JULIANNA MARGULIES

(Nurse Carol Hathaway)

Years in the ER: Six

Why we loved her: The curly hair played a role. A big one.

Life after the show: Starred in such stinker movies as Ghost Ship and Snakes on a Plane; had a brief affair with Tony Soprano on The Sopranos; worked on stage (The Vagina Monologues) and fronted a short-lived TV series on Fox (Canterbury’s Law).

THIS SEASON'S 'ER': John Stamos as Tony Gates, Maura Tierney as Dr. Abby Lockhart.

(Dr. Doug Ross)

Years in the ER: Six

Why we loved him: C’mon…must you ask?

Life after the show: C’mon…must you ask?

SHERRY STRINGFIELD

(Dr. Susan Lewis)

Years in the ER: Eight

Why we loved her: Her no-nonsense approach. The throaty voice, too.

Life after the show: Broke up with her boyfriend only a year after reportedly leaving ER to be with him; directed several plays; appeared in films (Autumn in New York; 54) and TV movies; had a recurring role in HBO’s Tell Me You Love Me.

MEDICAL TERMS WE’LL MISS HEARING THE MOST

1. STAT!: Slang expression for move your butt, doc!

2. Tox screen: Blood test to determine which drugs are in a patient’s system.

3. Intubation: The procedure of inserting a long tube (ouch!) into the trachea (that would be the wind pipe area) of a patient who isn’t breathing.

4. Triage: The system of prioritizing patients in an emergency situation where a whole bunch of people are hurt or sick. You know, it’s like taking a number at your local deli.

5. Code brown: Term for when a patient doesn’t make it to the bathroom in time. Uh, in the real world, we just use, “Ewwwwww.”

MEMORABLE GUEST STARS

OMAR EPPS as a stressed-out surgical intern who ends his stress by jumping in front of a train. (1997)

ALAN ALDA as a doctor suffering from Alzheimer’s. (2000)

SALLY FIELD as Abby Lockhart’s bipolar mom. (2001)

DON CHEADLE as a medical student with Parkinson’s disease. (2003)

HAL HOLBROOK as a hospice patient who has a huge influence on Luka’s life. (2008)